Transmission of yellow fever vaccine virus from breast feeding mothers to their infants: reporting of yellow fever virus (YFV) RNA detection in milk specimens

Tarteel Hassan; Razan A. Bashir; Dina N. Abdelrahman; Hassan Madni; Abdel Rahim M El Hussein; Isam M. Elkidir; Khalid A. Enan

doi:10.12688/f1000research.74576.4

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Brief Report

Revised

Transmission of yellow fever vaccine virus from breast feeding mothers to their infants: reporting of yellow fever virus (YFV) RNA detection in milk specimens

[version 4; peer review: 1 approved, 2 approved with reservations]

Tarteel Hassan¹, Razan A. Bashir¹, Dina N. Abdelrahman ¹, [...] Hassan Madni¹, Abdel Rahim M El Hussein¹, Isam M. Elkidir², Khalid A. Enan¹

Tarteel Hassan¹, Razan A. Bashir¹, [...] Dina N. Abdelrahman ¹, Hassan Madni¹, Abdel Rahim M El Hussein¹, Isam M. Elkidir², Khalid A. Enan¹

PUBLISHED 29 Feb 2024

Author details Author details

¹ Virology, Central Laboratory, Khartoum, Khartoum, Sudan
² Department of Microbiology and Parasitology, University of Khartoum, Khartoum, Khartoum, Sudan

Tarteel Hassan
Roles: Conceptualization, Investigation, Methodology, Visualization, Writing – Original Draft Preparation

Razan A. Bashir
Roles: Methodology, Visualization, Writing – Original Draft Preparation

Dina N. Abdelrahman
Roles: Validation, Visualization, Writing – Original Draft Preparation

Hassan Madni
Roles: Methodology

Abdel Rahim M El Hussein
Roles: Conceptualization, Supervision, Validation, Visualization, Writing – Review & Editing

Isam M. Elkidir
Roles: Conceptualization, Data Curation, Resources, Validation

Khalid A. Enan
Roles: Supervision, Validation, Visualization, Writing – Review & Editing

OPEN PEER REVIEW

REVIEWER STATUS

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Abstract

Background

Because of yellow fever’s serious impact on health, vaccination is the principal strategy to control the disease. Administration of the yellow fever vaccine to breastfeeding women should be before they complete 9 months post-delivery, in order to prevent transmission of the yellow fever vaccine virus to their infants through breast feeding. This study aimed to confirm whether the excretion of yellow fever vaccine virus is in milk of vaccinated breastfeeding mothers and to confirm the probable transmission to their infants through breast milk.

Methods

Samples were taken as follows: one serum specimen was taken 3-14 days after the date of the vaccination, and breast milk specimens were taken at four different time points between 3-4 days apart. Specimens were obtained from eight nursing mothers, who received the YVF vaccine (17DD). Mothers were asymptomatic before and after the vaccine administration but their infants developed symptoms after administration. Maternal serum samples were tested for YFV specific IgM antibodies through immuno-fluorescent assay (IFA). RNA was extracted from serum and breast milk specimens and YFV RNA screened using real-time polymerase chain reaction (RT-PCR).

Results

In total, five mothers (62.5%) were positive for YFV and two mothers (25%) had YFV RNA in serum. Among milk specimens, YFV RNA was detected during the four different mentioned collection times as follows (positive milk specimens/total milk specimens): 3/8 (37.5 %), 4/6 (66.6%) and 1/4(25%). RNA was completely undetectable in the last collection time.

Conclusions

YFV transmission from mothers to their babies through breast-feeding was highly probable indicated by the temporal relationship to mother’s YF vaccination.

Keywords

YFV, Vaccine, Milk, breast feeding mothers, Khartoum-Sudan

Corresponding author: Dina N. Abdelrahman

Competing interests: No competing interests were disclosed.

Grant information: The author(s) declared that no grants were involved in supporting this work.

Copyright: © 2024 Hassan T et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

How to cite: Hassan T, Bashir RA, Abdelrahman DN et al. Transmission of yellow fever vaccine virus from breast feeding mothers to their infants: reporting of yellow fever virus (YFV) RNA detection in milk specimens [version 4; peer review: 1 approved, 2 approved with reservations]. F1000Research 2024, 11:76 (https://doi.org/10.12688/f1000research.74576.4) First published: 21 Jan 2022, 11:76 (https://doi.org/10.12688/f1000research.74576.1) Latest published: 29 Feb 2024, 11:76 (https://doi.org/10.12688/f1000research.74576.4)

Revised Amendments from Version 3

The new version contains minor new addtions mainly in Table 1 and also in the limitations section in the discussion.

See the authors' detailed response to the review by Albert Koulman
See the authors' detailed response to the review by Ralph Huits

Introduction

The yellow fever virus is a mosquito-borne flavivirus that causes yellow fever,¹ a viral hemorrhagic fever that now occurs only in Africa, Central and South America,² but historically has had many wide outbreaks in Europe and North America.² Approximately 200,000 cases of yellow fever occur annually; 90% of them in Africa.² Yellow fever severity ranges from self-limited fever illness to hemorrhagic syndrome and death.³ Most yellow fever patients are asymptomatic, but 15% develop severe illness,⁴ which appears as a systemic illness that affects the liver (jaundice and necrosis), renal system, and myocardial system resulting in hemorrhage and shock.⁵ Among the 15% of patients that develop severe illness, the mortality rate is 20%–60%.⁴ Reports show that yellow fever is responsible for 29,000 to 60,000 deaths in South America and Africa every year, and it’s the most severe form of mosquito-borne diseases in tropical areas.¹

Because yellow fever is a potentially fatal disease, vaccination is the principal strategy to control the disease.⁴ An effective yellow fever 17DD vaccine was established in 1937, but there are still currently over 400 million unvaccinated people in the areas of high infection risk.¹

Live attenuated 17DD vaccine confers protection in more than 95% of recipients within a month after single dose vaccination. Its protection is attributed to both innate and adaptive immunity through production of neutralizing antibodies directly against the envelope protein. 17DD vaccine administration provides immunity for at least 10 years and probably can extend to give life-long immunity.⁶

The YFV vaccine can cause adverse side effects after its administration that range from mild to severe. The mild effects are headache, myalgia, and pain at the injection site, while severe effects can include anaphylactic shock, neurological diseases, and viscerotropic disease. The YFV vaccine is recommended to be administered after 9 months of age and from 6 months in endemic areas.⁷ Administration of the vaccine to breastfeeding women before 9 months post-delivery can transmit the yellow fever vaccine virus to their infants with high risk of neurological diseases. There are three case reports of confirmed transmission of the YFV vaccine strain from mothers to their infants through breastfeeding.⁸^–¹⁰ The first case reported that the mother received the yellow fever vaccine 15 days after her delivery, and she had symptoms of headache, malaise, and fever after 20-22 days.⁸ The other two cases reported that the mothers received a yellow fever vaccine, and their infants had developed encephalitis 3-4 weeks later.⁷^,⁹^,¹⁰

Many studies have reported the transmission and presence of other flaviviruses RNA in breast milk such as West Nile virus (WNV), Zika virus, dengue and chikungunya¹¹^–¹⁴; however, no previous study has reported the detection of YVF RNA in breast milk samples from vaccinated breast-feeding mothers in Sudan. Therefore, this study aimed to detect the yellow fever virus in breast milk and serum samples from vaccinated breastfeeding women whose infants got yellow fever illness to confirm whether the yellow fever vaccine virus is excreted and transmitted through breast milk. The mothers received the vaccine during an intensive YF vaccination campaign that involved millions of people in Khartoum State.

Methods

Ethical considerations

The study approved by the ministry of health, Sudan (approval number 5688-2019). Verbal consent was taken from mothers due to some being unlettered and some afraid of providing written consent. This was deemed adequate and approved by the Ministry of health.

Study design and population

This study involved YFV testing in serum and breast milk specimens from eight nursing mothers (aged from 20-33 years) from Khartoum, Sudan in November 2019. The mothers had received the YFV vaccine (17DD) (Bio-Manguinhos/Fiocruz) during the 2019 YFV vaccination program in Khartoum within 9 months of delivery. They were not showing any symptoms of YVF before they got the vaccines; however, their infants (ages from 45 days to 8 months) developed symptoms of fever, diarrhea, jaundice, vomiting, and/or skin rashes after one week from their mother received the vaccines. Participants were approached via telephone through reports provided to the Ministry of Health to follow-up individuals who experience complications after getting vaccinated.

Sample collection

The samples were collected by Ministry of health medical staff from participants in different hospital vaccination points. Blood samples were collected from mothers in a plain blood container, then serum separated from the blood sample through centrifugation at 1100 rpm for 15 minutes using centrifuge (Hettich- ZENTRIFUGEN), then serum samples pipetted into clean Eppendorf tubes and stored at -80°c until their use. Milk specimens were collected in a clean glass jar by hand expression whilst the infant was nursing on the other breast and vice versa. The specimens from the breasts (right and left) were expressed into separate clean glass jars. Collection of milk specimens performed on four occasions: the first collection time was 3-14 days from the date of the vaccination. The three following collections were 3-4 days apart. Milk specimens were collected on all occasions, but serum samples were collected only in the first collection.

Serology

Maternal serum samples were tested for YFV specific IgM antibodies using immuno-fluorescent assay (IFA) according to manufacturer instructions (Yellow fever virus IIFT (IgM), EUROIMMUN, Germany, catalogue number Fl 2665-1005 M).

RNA extraction

RNA was extracted from serum and breast milk specimens using a commercial RNA extraction kit (QIAamp viral RNA mini kit) according to the manufacturer instructions (Qiagen viral RNA, Germany). The extracted RNA was stored at −80°C until use.

Real-time polymerase chain reaction (PCR)

Detection of YFV RNA was performed using real-time PCR (Rotor 5 plex real-time PCR machine Qiagen, Germany). Commercial kit which developed to detect all YFV strains including vaccine strain (RealStar^® Yellow Fever Virus RT-PCR Kit 1.0, Germany) was used according to manufactures protocol. The PCR program consisted of 55°C for 20 min, 95°C for 2 min, followed by 45 cycles consisting of 95°C for 15 sec, 55°C for 45 sec and 72°C for 15 sec.

Statistical methods

No statistical analysis was needed. Data from participants were documented in an Excel sheet containing data for each mother and their infants. Rotor 5 plex real-time PCR thermo cycler software used to create Figure 3 while Figures 1 and 4 were created using word.

Results

The eight breast feeding mothers in Khartoum state were aged between 20 to 33 years old.¹⁵ Participation per each phase of the study shown in Figure 1.

Figure 1. Participation per each phase of the study.

Results of the first collection

Five mothers (62.5%) showed IgM antibodies against YFV using IFA technique (Figure 2). YFV RNA was detected by using real time PCR in 2/8 serum samples (25%) and 3/8 in breast milk (37.5%) (Table 1). Results of the PCR are shown in Figure 3.

Figure 2. Result of anti-YFV IgM using IFA technique.

(1) Positive sample for anti-YFV IgM, (2) Positive control for anti-YFV IgM, (3) negative control.

Table 1. Results of serological and molecular detection of YFV in milk and serum specimens.

Patient number	Phase between vaccination and first collection (days)	Time since delivery	IFA-IgM	RT-PCR (No of cycles/40)
				serum	Milk
					First		Second		Third		Fourth
					Right	Left	Right	Left	Right	Left	Right	Left
1	13	2.5 month	+	-	-	-	+ (36.2)	+ (34.1)	-	+ (34.6)	-	-
2	12	2 months	+	-	-	-	+ (34.8)	+ (40.0)	-	-	-	-
3	10	7 months	-	-	+ (39.7)	+ (38.9)	+ (34.6)	-	-	-	-	-
4	11	45 day	+	-	-	-	-	-	NA*	NA*	NA*	NA*
5	4	5 months	-	+ (37.3)	+ (36.4)	-	+ (36.4)	-	-	-	NA*	NA*
6	5	2 months	-	-	-	-	-	-	NA*	NA*	NA*	NA*
7	12	8 months	+	-	-	+ (34.2)	NA*	NA*	NA*	NA*	NA*	NA*
8	14	7 months	+	+ (32.8)	-	-	NA*	NA*	NA*	NA*	NA*	NA*

PCR = polymerase chain reaction; YFV = yellow fever virus.

* Means no sample obtained.

Figure 3. Real time polymerase chain reaction (PCR) result for yellow fever virus (YFV) positive milk specimens.

Results of the second collection

In this phase, only 6 samples were obtained, among them YFV RNA was demonstrated in 4/6 (66.6%) breast milk specimens (Table 1).

Results of the third collection

Four mothers were enrolled in this occasion. Only 1/4 (25%) of the milk samples (25%) was positive for YFV RNA (Table 1).

Results of the fourth collection

Milk specimens were obtained from 3 mothers, all specimens showed negative result for YFV RNAs (Table 1). Minimal clearance of the viral RNA in milk was 11 day after vaccination and the maximum time needed for the clearance was 24 days after vaccine administration.

Real-time PCR results showed in Figure 1 and results of yellow fever virus (YFV) detection among different collection dates showed in Figure 4.

Figure 4. Result of yellow fever virus (YFV) detection among different collection dates.

Discussion

According to the applied recommendations for YF vaccine, breast-feeding mothers and their infants who are aged less than 9 months should avoid YF vaccination. However, when breastfeeding mothers must travel to a yellow fever–endemic area, these women should be vaccinated,¹⁶ and its recommended to temporary interrupt brestfeeding for at least 2 weeks after YFV vaccination¹⁷ while in contrast, this study show that needed time to insure complete interrupted shedding of the virus in milk is up 24 days after vaccine administration. In a CDC report, the prenatal transmission of vaccine strain was demonstrated without RNA detection in the milk samples, in other side our study proves the transmission that by RNA detection in milk samples.¹⁸

This current study was the first study to detect YFV through detection of RNA in milk samples from vaccinated nursing mothers. In contrast a study by Eder Fernandes (2020), reported that YFV RNA was not detected in serum and milk samples from vaccinated lactating mother.¹⁹

Between 2009 and 2020, YFV RNA was usually detected in samples other than milk such as CSF and serum. On the other hand, in April 2009 the first case of YF vaccine strain transmission through breast milk was reported in a Brazilian infant; yellow fever-specific IgM antibodies were detected in serum and CSF and yellow fever vaccine strain viral RNA was found in CSF of the infant. However, no breast milk or maternal serum was collected for yellow fever virus testing.

On March 2011, another case report study showed a baby was developing encephalitis after his mother had received the YFV vaccine when he was 10 days old.¹⁰ The authors claimed the probable transmission of the vaccine virus from the mother to her baby by detecting YF IgM in the infant’s serum and CSF. The clinical presentation, temporal relationship to the mother’s vaccination, and lack of other alternative pathogens were also strongly supportive of acute central nervous system infection with the vaccine strain of yellow fever.¹⁰

Yet another study reported on detection of YFV IgM in a 38 days-old infant’s serum and CSF who was exclusively being breast-fed. The baby suffered from meningoencephalitis 3 to 4 weeks after the YFV vaccine administration to his mother.⁹^,¹⁰ The baby was discharged after the convulsive crises were controlled.

Many studies have reported on the detection of flaviviruses RNA (Zika, West Nile, dengue, and chikungunya) in human milk.⁷ A study in 2017 described detection of viral RNA in serum and milk of three symptomatic breast-feeding mothers who were infected with Zika virus.¹³ And in another study WNV RNA and IgM antibodies were detected in breast milk samples from mothers whose babies developed West Nile virus.¹⁴ In one case of vertical transmission of dengue infection, the RNA of the virus was detected in blood samples from a mother and her child as well as in the mother’s breast milk.¹¹ Furthermore, another study reported that chikungunya virus RNA was detected in serum, urine and milk samples of a breast-feeding mother at third day of symptoms onset.¹²

According to the previous reports of Yellow fever, all 3 reported cases of yellow fever were engaged to the vaccine virus strain, and in all reported cases RNA was not detected in breast milk. None of the reported cases was confirm detection of the virus in breast milk specimen, the only confirmed infection through viral RNA PCR detection was in cerebrospinal fluid of infant after his mother received vaccine, while in the other cases; serological detection of YFV IgM antibodies was performed in serum and cerebrospinal fluid.²⁰ Also Eder Gatti (2020), reported that YFV RNA was not detected in serum and milk samples from vaccinated lactating mother while specific IgM was detected.¹⁹ It is important to mention that human milk’s cellular composition is dynamic, and a variety of circumstances, including the stage of lactation, health, and child feeding, can alter the quantity of various cell types during the lactation period.²¹

This current study was the first study to confirm detection of YFV vaccine strain, through detection of RNA in milk samples from vaccinated nursing mothers. In contrast a case study reported by Ana Freitas (2020), showed detection of wild type YFV RNA genome in breast milk specimens from the mother.²⁰ Through searching it was un-able to find a report showing YFV vaccine strain presence in milk as we report.

This study has some limitations; because objections by mothers, no samples were collected from the infants in order to exclude other causes of the observed illness and to rule out an asymptomatic transmission of the virus. Also serum samples need to be collected through the other phases in order to follow the viral existence. Another limitation is that the detected YFV RNA must be sequenced to confirm the identity as 17DD vaccine strain.

Conclusion

Despite limitations, this study proves that YFV transmission from mothers to their babies through breast-feeding was highly probable indicated by the temporal relationship to mother’s YF vaccination. This also represents the first report on the detection of YFV RNA in human milk after YF vaccination in Sudan.

Data availability

Underlying data

Figshare: Transmission of yellow fever vaccine virus from breast feeding mothers to their infants: reporting of yellow fever virus (YFV) RNA detection in milk specimens. https://doi.org/10.6084/m9.figshare.17206640.¹⁵

Data are available under the terms of the Creative Commons Attribution 4.0 International license (CC-BY 4.0).

References

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2. Barnett ED: Yellow fever: epidemiology and prevention. Clin. Infect. Dis. 2007; 44(6): 850–856. Publisher Full Text
3. Romano APM, Costa ZGA, Ramos DG, et al.: Yellow fever outbreaks in unvaccinated populations, Brazil, 2008–2009. PLoS Negl. Trop. Dis. 2014; 8(3): e2740. PubMed Abstract | Publisher Full Text
4. Hamer DH, Angelo K, Caumes E, et al.: Fatal yellow fever in travelers to Brazil, 2018. Morb. Mortal. Wkly Rep. 2018; 67(11): 340–341. PubMed Abstract | Publisher Full Text
5. Monath TP: Dengue and yellow fever—challenges for the development and use of vaccines. N. Engl. J. Med. 2007; 357(22): 2222–2225. PubMed Abstract | Publisher Full Text
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7. Mann TZ, Haddad LB, Williams TR, et al.: Breast milk transmission of flaviviruses in the context of Zika virus: a systematic review. Paediatr. Perinat. Epidemiol. 2018; 32(4): 358–368. PubMed Abstract | Publisher Full Text
8. Couto A, Salomão M, Schermann M, et al.: Transmission of yellow fever vaccine virus through breast-feeding-Brazil, 2009. Morb. Mortal. Wkly Rep. 2010; 59(5): 130–132.
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11. Barthel A, Gourinat A-C, Cazorla C, et al.: Breast milk as a possible route of vertical transmission of dengue virus? Clin. Infect. Dis. 2013; 57(3): 415–417. PubMed Abstract | Publisher Full Text
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14. Hinckley AF, O’Leary DR, Hayes EB: Transmission of West Nile virus through human breast milk seems to be rare. Pediatrics. 2007; 119(3): e666–e671. PubMed Abstract | Publisher Full Text
15. Bashir R, Hassan T, Abdelrahman N, et al.: Transmission of yellow fever vaccine virus from breast feeding mothers to their infants: reporting of yellow fever virus (YFV) RNA detection in milk specimens. figshare. Dataset. 2021. Publisher Full Text
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Comments on this article Comments (1)

Version 4

VERSION 4 PUBLISHED 29 Feb 2024

Revised

Comment

Version 1

VERSION 1 PUBLISHED 21 Jan 2022

Discussion is closed on this version, please comment on the latest version above.

Author Response 15 Mar 2022

Dina Naser, Virology, Central Laboratory, Khartoum, Sudan

15 Mar 2022

Author Response
Comments

Major comment:
The mentioned edits has been reviewed and corrected in the draft. At that time in 2019, there were different arboviral outbreaks in many regions in Sudan, ... Continue reading
Comments

Major comment:
The mentioned edits has been reviewed and corrected in the draft. At that time in 2019, there were different arboviral outbreaks in many regions in Sudan, as a response to that, the ministry of health start a preventive vaccination campaign against YVF.

Minor comments:

- Introduction:

Done

- Method

What were the inclusion criteria? How were these woman selected?

Eight nursing mothers who had received the YFV vaccine (17DD) during the 2019 YFV vaccination program in Khartoum within 9 months of delivery.

What is the cut-off CT-value for q-PCR result to be considered positive?

Results obtained according to the used rt-PCR kit.

Was a negative control included to check for contamination?

Yes of course.

What was the positive control for the YFV PCR?

Positive controls already included with the kits reagent.

- Results

Results showed in tables presented into single table, while it will be difficult to understand results showed in figures if they presented in one figure.

- Discussion

Changes have been made in the draft.
Comments

Major comment:
The mentioned edits has been reviewed and corrected in the draft. At that time in 2019, there were different arboviral outbreaks in many regions in Sudan, as a response to that, the ministry of health start a preventive vaccination campaign against YVF.

Minor comments:

- Introduction:

Done

- Method

What were the inclusion criteria? How were these woman selected?

Eight nursing mothers who had received the YFV vaccine (17DD) during the 2019 YFV vaccination program in Khartoum within 9 months of delivery.

What is the cut-off CT-value for q-PCR result to be considered positive?

Results obtained according to the used rt-PCR kit.

Was a negative control included to check for contamination?

Yes of course.

What was the positive control for the YFV PCR?

Positive controls already included with the kits reagent.

- Results

Results showed in tables presented into single table, while it will be difficult to understand results showed in figures if they presented in one figure.

- Discussion

Changes have been made in the draft.
Competing Interests: No competing interests Close
Report a concern
Discussion is closed on this version, please comment on the latest version above.

Author details Author details

¹ Virology, Central Laboratory, Khartoum, Khartoum, Sudan
² Department of Microbiology and Parasitology, University of Khartoum, Khartoum, Khartoum, Sudan

Tarteel Hassan
Roles: Conceptualization, Investigation, Methodology, Visualization, Writing – Original Draft Preparation

Razan A. Bashir
Roles: Methodology, Visualization, Writing – Original Draft Preparation

Dina N. Abdelrahman
Roles: Validation, Visualization, Writing – Original Draft Preparation

Hassan Madni
Roles: Methodology

Abdel Rahim M El Hussein
Roles: Conceptualization, Supervision, Validation, Visualization, Writing – Review & Editing

Isam M. Elkidir
Roles: Conceptualization, Data Curation, Resources, Validation

Khalid A. Enan
Roles: Supervision, Validation, Visualization, Writing – Review & Editing

Competing interests

No competing interests were disclosed.

Grant information

The author(s) declared that no grants were involved in supporting this work.

Article Versions (4)

version 4

Revised

Published: 29 Feb 2024, 11:76

https://doi.org/10.12688/f1000research.74576.4

version 3

Revised

Published: 20 Jul 2022, 11:76

https://doi.org/10.12688/f1000research.74576.3

version 2

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Published: 15 Mar 2022, 11:76

https://doi.org/10.12688/f1000research.74576.2

version 1

Published: 21 Jan 2022, 11:76

https://doi.org/10.12688/f1000research.74576.1

© 2024 Hassan T et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Hassan T, Bashir RA, Abdelrahman DN et al. Transmission of yellow fever vaccine virus from breast feeding mothers to their infants: reporting of yellow fever virus (YFV) RNA detection in milk specimens [version 4; peer review: 1 approved, 2 approved with reservations]. F1000Research 2024, 11:76 (https://doi.org/10.12688/f1000research.74576.4)

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ApprovedThe paper is scientifically sound in its current form and only minor, if any, improvements are suggested

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Version 3

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Reviewer Report 15 Dec 2023

Albert Koulman, Core Metabolomics and Lipidomics Laboratory, Wellcome Trust-MRC Institute of Metabolic Science, Addenbrooke's Treatment Centre, University of Cambridge, Cambridge, UK

Approved with Reservations

https://doi.org/10.5256/f1000research.134910.r224060

One of the limitations is the sometimes very low concentrations of RNA. It is clear that for some of the samples, the detection threshold is reached between 30 and 35 cycles, while for other samples it is between 35 and 40 cycles. This means that the RNA concentrations are very low, at a level that contamination might be an issue. It is also questionable if such low concentrations are biologically meaningful. It would be good if the authors could provide the number of cycles necessary to reach the threshold for each sample. Is there exact information on the day the samples were collected? Please provide this information in Table 1. Please also provide information on the stages of breastfeeding. At the moment there is only mention of “within 9 months of delivery”, please provide at least the number of months since delivery for each mother.
If the serum is negative for the RT-PCR test and negative for the IgM assay, it becomes difficult to understand why or how the milk became positive.
The authors should also elaborate on the limitation section. It is important to note that the lactation changes and that the amount and type of cells and material in the milk will change during the whole lactation period. It could be that in early lactation the change of viral RNA getting into the milk is higher than in the later stages of lactation. Also, highlight that the concentration of RNA needs to be taken into account when assessing any risks for the infant.

Is the work clearly and accurately presented and does it cite the current literature?

Yes
Is the study design appropriate and is the work technically sound?

Partly
Are sufficient details of methods and analysis provided to allow replication by others?

Yes
If applicable, is the statistical analysis and its interpretation appropriate?

Not applicable
Are all the source data underlying the results available to ensure full reproducibility?

Partly
Are the conclusions drawn adequately supported by the results?

Partly

Competing Interests: No competing interests were disclosed.

Reviewer Expertise: lactation research and analytical chemistry

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.

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Author Response 13 Apr 2024

Dina Naser, Virology, Central Laboratory, Khartoum, Sudan

13 Apr 2024

Author Response

Dear Albert Koulman, your valuable comments are highly appreciated.

Regarding the variety in RNA concentrations, the mothers' varying vaccination time are the reason for the variation in RNA concentrations. ... Continue reading Dear Albert Koulman, your valuable comments are highly appreciated.

Regarding the variety in RNA concentrations, the mothers' varying vaccination time are the reason for the variation in RNA concentrations. All safety measures to avoid contamination or influences on the results were implemented during the testing process, including performing a negative extraction control with the samples to ensure the accuracy of the results. In addition to strict testing procedures and repetitive testing, the lactating mothers are mistakenly administered the YFV vaccination during a period when it is advised to avoid it. As a result, every identified RNA is seen to be physiologically important and significant.

Table 1 modified with your suggested additions, the number of months since delivery for each mother and the number of cycles necessary to reach the threshold for each sample.

The explanation for the statement, "If the serum is negative for the RT-PCR test and negative for the IgM assay, it becomes difficult to understand why or how the milk became positive", could be that most of the serum samples were collected after more than 10 days from vaccination date and it is suspected that milk samples was taken before the virus had completely cleared in milk, because phase-to-phase collection intervals take three days, and subsequent phases additionally show negative YFV RNA detection.
Dear Albert Koulman, your valuable comments are highly appreciated.

Regarding the variety in RNA concentrations, the mothers' varying vaccination time are the reason for the variation in RNA concentrations. All safety measures to avoid contamination or influences on the results were implemented during the testing process, including performing a negative extraction control with the samples to ensure the accuracy of the results. In addition to strict testing procedures and repetitive testing, the lactating mothers are mistakenly administered the YFV vaccination during a period when it is advised to avoid it. As a result, every identified RNA is seen to be physiologically important and significant.

Table 1 modified with your suggested additions, the number of months since delivery for each mother and the number of cycles necessary to reach the threshold for each sample.

The explanation for the statement, "If the serum is negative for the RT-PCR test and negative for the IgM assay, it becomes difficult to understand why or how the milk became positive", could be that most of the serum samples were collected after more than 10 days from vaccination date and it is suspected that milk samples was taken before the virus had completely cleared in milk, because phase-to-phase collection intervals take three days, and subsequent phases additionally show negative YFV RNA detection.
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Author Response 13 Apr 2024

Dina Naser, Virology, Central Laboratory, Khartoum, Sudan

13 Apr 2024

Author Response

Dear Albert Koulman, your valuable comments are highly appreciated.

Regarding the variety in RNA concentrations, the mothers' varying vaccination time are the reason for the variation in RNA concentrations. ... Continue reading Dear Albert Koulman, your valuable comments are highly appreciated.

Regarding the variety in RNA concentrations, the mothers' varying vaccination time are the reason for the variation in RNA concentrations. All safety measures to avoid contamination or influences on the results were implemented during the testing process, including performing a negative extraction control with the samples to ensure the accuracy of the results. In addition to strict testing procedures and repetitive testing, the lactating mothers are mistakenly administered the YFV vaccination during a period when it is advised to avoid it. As a result, every identified RNA is seen to be physiologically important and significant.

Table 1 modified with your suggested additions, the number of months since delivery for each mother and the number of cycles necessary to reach the threshold for each sample.

The explanation for the statement, "If the serum is negative for the RT-PCR test and negative for the IgM assay, it becomes difficult to understand why or how the milk became positive", could be that most of the serum samples were collected after more than 10 days from vaccination date and it is suspected that milk samples was taken before the virus had completely cleared in milk, because phase-to-phase collection intervals take three days, and subsequent phases additionally show negative YFV RNA detection.
Dear Albert Koulman, your valuable comments are highly appreciated.

Regarding the variety in RNA concentrations, the mothers' varying vaccination time are the reason for the variation in RNA concentrations. All safety measures to avoid contamination or influences on the results were implemented during the testing process, including performing a negative extraction control with the samples to ensure the accuracy of the results. In addition to strict testing procedures and repetitive testing, the lactating mothers are mistakenly administered the YFV vaccination during a period when it is advised to avoid it. As a result, every identified RNA is seen to be physiologically important and significant.

Table 1 modified with your suggested additions, the number of months since delivery for each mother and the number of cycles necessary to reach the threshold for each sample.

The explanation for the statement, "If the serum is negative for the RT-PCR test and negative for the IgM assay, it becomes difficult to understand why or how the milk became positive", could be that most of the serum samples were collected after more than 10 days from vaccination date and it is suspected that milk samples was taken before the virus had completely cleared in milk, because phase-to-phase collection intervals take three days, and subsequent phases additionally show negative YFV RNA detection.
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Version 2

VERSION 2

PUBLISHED 15 Mar 2022

Revised

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Reviewer Report 20 May 2022

Ralph Huits, Department of Infectious Tropical diseases and Microbiology, IRCCS Ospedale Sacro Cuore Don Calabria, Negrar, Italy

Approved with Reservations

https://doi.org/10.5256/f1000research.122300.r129788

This manuscript reports on the testing of maternal serum for YFV specific IgM antibodies and YFV RNA, and serial breast milk samples for detectable YFV RNA, in eight nursing mothers, whose infants developed symptoms after the mothers received YVF vaccine. The authors found, for the first time, YFV RNA in breastmilk in five out of eight mothers 4-24 days after receiving 17DD vaccine. The detectable shedding of YFV (probably vaccine strain) in breast milk is the main message of this manuscript. This is an important finding that contributes to the evidence base for current YFV vaccination practices.

Major comments:

How were the mothers selected? It appears they were examined because their infants fell ill. This should be stated unambiguously, as it may underestimate the YFV RNA detection (and transmissibility) in breast milk.

Strictly speaking, transmission was not confirmed, because no diagnostic data was presented for the infants.

Minor comments:

Introduction: (End of 1^st paragraph): 'the most severe form (?)', suggest rephrasing, e.g., ‘…, making it the most severe of mosquito-borne diseases.'

The section on published case reports should include ref. 18.

(Also note: ref. 9 = ref. 20, cited twice)

Fig. 1: check spelling

Results section: list the percentages after the nouns (e.g., 2 serum samples (25%)); In reporting the PCR results obtained in the second, third and fourth collections of breast milk, I would favour expressing the positive results as a fraction with the number of patients tested per timepoint in the denominator (e.g., 3/8, 4/6, etc.), rather than percentages that (falsely) lead back to the original number of patients (n=8).

Table 1: Column headings: ‘Sample number’ should be ‘patient number’; ‘Date’ should be date of YFV vaccination’; For clarity it is probably more relevant to list the number of days between vaccination and timing of first sample collection, instead of the columns 2 & 3. Do ‘Right’/ ‘Left’ column headings refer to the right/left mamma? Please explain in legend.

Fig. 3: check spelling; data in ‘YFV RNA in breast milk’ and ‘… in serum’ are not consistent with Table 1.

Discussion: It is hard to ascertain whether recommendations are ‘universally applied’; the statement needs a reference. The reference for a 2-week interruption of breastfeeding before YFV vaccination is expert opinion. Could the authors comment on this duration based on their findings? (Detectable RNA in breastmilk up to 24 days post vaccination?)

The CDC report cited (ref. 18) does confirm detection of YFV vaccine in the infant’s CSF. I suggest rephrasing. I have 2 comments on the statement ‘This current study was the first…’: this study was not the first, see ref. 18 above and in the next paragraph of the text- ref. 18 was not a probable, but a confirmed case.

For Eder Gatti (2020): their surname is Fernandes. (Repeating findings from this paper on p. 8 is redundant).

Is the work clearly and accurately presented and does it cite the current literature?

Partly
Is the study design appropriate and is the work technically sound?

Partly
Are sufficient details of methods and analysis provided to allow replication by others?

Yes
If applicable, is the statistical analysis and its interpretation appropriate?

Not applicable
Are all the source data underlying the results available to ensure full reproducibility?

No source data required
Are the conclusions drawn adequately supported by the results?

Partly

Competing Interests: No competing interests were disclosed.

Reviewer Expertise: Arbovirus infections, malaria, tropical medicine, diagnostics evaluation.

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Author Response 20 Jul 2022

Dina Naser, Virology, Central Laboratory, Khartoum, Sudan

20 Jul 2022

Author Response

Dear Ralph Huits,

Major comment:
The selected mothers had received the YFV vaccine within 9 months of delivery. They were not showing any symptoms of YVF before they got ... Continue reading Dear Ralph Huits,

Major comment:
The selected mothers had received the YFV vaccine within 9 months of delivery. They were not showing any symptoms of YVF before they got the vaccines; however, their infants developed symptoms of fever, diarrhea, jaundice, vomiting, and/or skin rashes after one week from their mother received the vaccines.

Transmission to infants was confirmed through that their mothers get vaccinated week before developing symptoms and also through the detected YFV RNA in milk specimens from these same mothers during the infant’s appeared symptoms.

Minor comments:

Result:

Do ‘Right’/ ‘Left’ column headings refer to the right/left mamma?

Yes, milk samples collected from both breasts in order to get the most excreted YFV in milk and also to study if there is any relation or correlation between breast side and YFV shedding in milk.

*Other reviewer edits are done in the new submitted version.*
Dear Ralph Huits,

Major comment:
The selected mothers had received the YFV vaccine within 9 months of delivery. They were not showing any symptoms of YVF before they got the vaccines; however, their infants developed symptoms of fever, diarrhea, jaundice, vomiting, and/or skin rashes after one week from their mother received the vaccines.

Transmission to infants was confirmed through that their mothers get vaccinated week before developing symptoms and also through the detected YFV RNA in milk specimens from these same mothers during the infant’s appeared symptoms.

Minor comments:

Result:

Do ‘Right’/ ‘Left’ column headings refer to the right/left mamma?

Yes, milk samples collected from both breasts in order to get the most excreted YFV in milk and also to study if there is any relation or correlation between breast side and YFV shedding in milk.

*Other reviewer edits are done in the new submitted version.*
Competing Interests: No competing interest. Close
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Author Response 22 Jun 2022

Dina Naser, Virology, Central Laboratory, Khartoum, Sudan

22 Jun 2022

Author Response

In addition, some changes have been made in table, these changes are topical to that addressed online by the reviewer.
Competing Interests: No competing interest.
In addition, some changes have been made in table, these changes are topical to that addressed online by the reviewer.
In addition, some changes have been made in table, these changes are topical to that addressed online by the reviewer.
Competing Interests: No competing interest. Close
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COMMENTS ON THIS REPORT

Author Response 20 Jul 2022

Dina Naser, Virology, Central Laboratory, Khartoum, Sudan

20 Jul 2022

Author Response

Dear Ralph Huits,

Major comment:
The selected mothers had received the YFV vaccine within 9 months of delivery. They were not showing any symptoms of YVF before they got ... Continue reading Dear Ralph Huits,

Major comment:
The selected mothers had received the YFV vaccine within 9 months of delivery. They were not showing any symptoms of YVF before they got the vaccines; however, their infants developed symptoms of fever, diarrhea, jaundice, vomiting, and/or skin rashes after one week from their mother received the vaccines.

Transmission to infants was confirmed through that their mothers get vaccinated week before developing symptoms and also through the detected YFV RNA in milk specimens from these same mothers during the infant’s appeared symptoms.

Minor comments:

Result:

Do ‘Right’/ ‘Left’ column headings refer to the right/left mamma?

Yes, milk samples collected from both breasts in order to get the most excreted YFV in milk and also to study if there is any relation or correlation between breast side and YFV shedding in milk.

*Other reviewer edits are done in the new submitted version.*
Dear Ralph Huits,

Major comment:
The selected mothers had received the YFV vaccine within 9 months of delivery. They were not showing any symptoms of YVF before they got the vaccines; however, their infants developed symptoms of fever, diarrhea, jaundice, vomiting, and/or skin rashes after one week from their mother received the vaccines.

Transmission to infants was confirmed through that their mothers get vaccinated week before developing symptoms and also through the detected YFV RNA in milk specimens from these same mothers during the infant’s appeared symptoms.

Minor comments:

Result:

Do ‘Right’/ ‘Left’ column headings refer to the right/left mamma?

Yes, milk samples collected from both breasts in order to get the most excreted YFV in milk and also to study if there is any relation or correlation between breast side and YFV shedding in milk.

*Other reviewer edits are done in the new submitted version.*
Competing Interests: No competing interest. Close
Report a concern
Author Response 22 Jun 2022

Dina Naser, Virology, Central Laboratory, Khartoum, Sudan

22 Jun 2022

Author Response

In addition, some changes have been made in table, these changes are topical to that addressed online by the reviewer.
Competing Interests: No competing interest.
In addition, some changes have been made in table, these changes are topical to that addressed online by the reviewer.
In addition, some changes have been made in table, these changes are topical to that addressed online by the reviewer.
Competing Interests: No competing interest. Close
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Reviewer Report 22 Mar 2022

Leo G Visser, Department of Infectious Diseases, Leiden Medical University Center, Leiden, The Netherlands

Approved

https://doi.org/10.5256/f1000research.122300.r127591

The authors have addressed the concerns ... Continue reading

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Version 1

VERSION 1

PUBLISHED 21 Jan 2022

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Reviewer Report 07 Feb 2022

Leo G Visser, Department of Infectious Diseases, Leiden Medical University Center, Leiden, The Netherlands

Approved with Reservations

https://doi.org/10.5256/f1000research.78349.r120678

The authors report for the first time the presence of YVF RNA in breast milk specimens of five out of eight woman, three to fourteen days after receiving 17DD during vaccination campaign in Khartoum, Sudan.

Major comment

Although transmission of YFV-17DD to the neonate through breastfeeding has been demonstrated before,¹ attempts to isolate the vaccine strain from breast milk have been unsuccessful.²

On the other hand, wild YFV has been detected in breast milk before.³ Although there were no reports of a yellow fever outbreak in Khartoum state in November 2019, final proof would require to demonstrate that the nucleotide sequence of the amplified PCR product in the breast milk was identical to 17DD yellow fever vaccine virus. This limitation should be addressed in the discussion.

Minor comments

Introduction:

The line “Administration of the vaccine to breastfeeding women before 9 months post-delivery can transmit the yellow fever vaccine virus to their infants through breast milk.” is confusing: breastfeeding is a risk factor for transmission irrespective of time post-delivery. However, the risk of YFV-associated neurological disease after transmission may occur in infants less than 6-9 months of age. The sentence should be corrected accordingly.

Method:

What were the inclusion criteria? How were these woman selected? What is the cut-off CT-value for q-PCR result to be considered positive? Was a negative control included to check for contamination? What was the positive control for the YFV PCR?

Results

Presentation of the results in a single table would increase readability. The data provided in Figures 1 and 4, and Tables 1 and 2 could be compiled into one table (time and specimen in the upper row, and subjects in left column). Figure 2 is redundant.

In Figure 3 it is not clear from which specimen the amplification curves are presented? Is this serum or breast milk? The CT-values of 32 - 40 indicate very low levels of viral RNA. Maybe the authors could provide some more information on the CT-values in serum and breast milk.

Discussion

Could the authors elaborate on how many weeks breast feeding should be interrupted to prevent transmission to the infant?
The authors should discuss on the lack of confirmation that the nucleotide sequence of the amplified PCR product in the breast milk was identical to 17DD yellow fever vaccine virus.

Is the work clearly and accurately presented and does it cite the current literature?

Yes
Is the study design appropriate and is the work technically sound?

Partly
Are sufficient details of methods and analysis provided to allow replication by others?

Yes
If applicable, is the statistical analysis and its interpretation appropriate?

Not applicable
Are all the source data underlying the results available to ensure full reproducibility?

No source data required
Are the conclusions drawn adequately supported by the results?

Partly

References

1. Centers for Disease Control and Prevention CDC: Transmission of yellow fever vaccine virus through breast-feeding - Brazil, 2009.MMWR Morb Mortal Wkly Rep. 2010; 59 (5): 130-2 PubMed Abstract
2. Fernandes EG, Nogueira JS, Porto VBG, Sato HK: The search for yellow fever virus vaccine in breast milk of inadvertently vaccinated women in Brazil.Rev Inst Med Trop Sao Paulo. 2020; 62: e33 PubMed Abstract | Publisher Full Text
3. Ribeiro AF, Brasil LMCR, Prada RM, Nogueira JS, et al.: Detection of Wild-type Yellow Fever Virus in Breast Milk.Pediatr Infect Dis J. 39 (1): 68-69 PubMed Abstract | Publisher Full Text

Competing Interests: No competing interests were disclosed.

Reviewer Expertise: Vaccine immunology, alternative vaccination routes, yellow fever vaccine, rabies vaccine, mRNA 1273

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Version 4

VERSION 4 PUBLISHED 29 Feb 2024

Revised

Comment

Version 1

VERSION 1 PUBLISHED 21 Jan 2022

Discussion is closed on this version, please comment on the latest version above.

Author Response 15 Mar 2022

Dina Naser, Virology, Central Laboratory, Khartoum, Sudan

15 Mar 2022

Author Response
Comments

Major comment:
The mentioned edits has been reviewed and corrected in the draft. At that time in 2019, there were different arboviral outbreaks in many regions in Sudan, ... Continue reading
Comments

Major comment:
The mentioned edits has been reviewed and corrected in the draft. At that time in 2019, there were different arboviral outbreaks in many regions in Sudan, as a response to that, the ministry of health start a preventive vaccination campaign against YVF.

Minor comments:

- Introduction:

Done

- Method

What were the inclusion criteria? How were these woman selected?

Eight nursing mothers who had received the YFV vaccine (17DD) during the 2019 YFV vaccination program in Khartoum within 9 months of delivery.

What is the cut-off CT-value for q-PCR result to be considered positive?

Results obtained according to the used rt-PCR kit.

Was a negative control included to check for contamination?

Yes of course.

What was the positive control for the YFV PCR?

Positive controls already included with the kits reagent.

- Results

Results showed in tables presented into single table, while it will be difficult to understand results showed in figures if they presented in one figure.

- Discussion

Changes have been made in the draft.
Comments

Major comment:
The mentioned edits has been reviewed and corrected in the draft. At that time in 2019, there were different arboviral outbreaks in many regions in Sudan, as a response to that, the ministry of health start a preventive vaccination campaign against YVF.

Minor comments:

- Introduction:

Done

- Method

What were the inclusion criteria? How were these woman selected?

Eight nursing mothers who had received the YFV vaccine (17DD) during the 2019 YFV vaccination program in Khartoum within 9 months of delivery.

What is the cut-off CT-value for q-PCR result to be considered positive?

Results obtained according to the used rt-PCR kit.

Was a negative control included to check for contamination?

Yes of course.

What was the positive control for the YFV PCR?

Positive controls already included with the kits reagent.

- Results

Results showed in tables presented into single table, while it will be difficult to understand results showed in figures if they presented in one figure.

- Discussion

Changes have been made in the draft.
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Leo G Visser, Leiden Medical University Center, Leiden, The Netherlands
Ralph Huits, IRCCS Ospedale Sacro Cuore Don Calabria, Negrar, Italy
Albert Koulman, University of Cambridge, Cambridge, UK

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Reviewer Report

10 Views

15 Dec 2023 | for Version 3

Albert Koulman, Core Metabolomics and Lipidomics Laboratory, Wellcome Trust-MRC Institute of Metabolic Science, Addenbrooke's Treatment Centre, University of Cambridge, Cambridge, UK

10 Views Cite this report Responses(1)

Approved With Reservations

Is the work clearly and accurately presented and does it cite the current literature?

Yes
Is the study design appropriate and is the work technically sound?

Partly
Are sufficient details of methods and analysis provided to allow replication by others?

Yes
If applicable, is the statistical analysis and its interpretation appropriate?

Not applicable
Are all the source data underlying the results available to ensure full reproducibility?

Partly
Are the conclusions drawn adequately supported by the results?

Partly

Competing Interests

No competing interests were disclosed.

Reviewer Expertise

lactation research and analytical chemistry

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Responses (1)

Author Response

13 Apr 2024

Dina Naser, Virology, Central Laboratory, Khartoum, Sudan

Dear Albert Koulman, your valuable comments are highly appreciated.

Regarding the variety in RNA concentrations, the mothers' varying vaccination time are the reason for the variation in RNA concentrations. All safety measures to avoid contamination or influences on the results were implemented during the testing process, including performing a negative extraction control with the samples to ensure the accuracy of the results. In addition to strict testing procedures and repetitive testing, the lactating mothers are mistakenly administered the YFV vaccination during a period when it is advised to avoid it. As a result, every identified RNA is seen to be physiologically important and significant.

Table 1 modified with your suggested additions, the number of months since delivery for each mother and the number of cycles necessary to reach the threshold for each sample.

The explanation for the statement, "If the serum is negative for the RT-PCR test and negative for the IgM assay, it becomes difficult to understand why or how the milk became positive", could be that most of the serum samples were collected after more than 10 days from vaccination date and it is suspected that milk samples was taken before the virus had completely cleared in milk, because phase-to-phase collection intervals take three days, and subsequent phases additionally show negative YFV RNA detection.

View more View less

Competing Interests

No competeing intrests

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Reviewer Report

16 Views

20 May 2022 | for Version 2

Ralph Huits, Department of Infectious Tropical diseases and Microbiology, IRCCS Ospedale Sacro Cuore Don Calabria, Negrar, Italy

16 Views Cite this report Responses(2)

Approved With Reservations

Is the work clearly and accurately presented and does it cite the current literature?

Partly
Is the study design appropriate and is the work technically sound?

Partly
Are sufficient details of methods and analysis provided to allow replication by others?

Yes
If applicable, is the statistical analysis and its interpretation appropriate?

Not applicable
Are all the source data underlying the results available to ensure full reproducibility?

No source data required
Are the conclusions drawn adequately supported by the results?

Partly

Competing Interests

No competing interests were disclosed.

Reviewer Expertise

Arbovirus infections, malaria, tropical medicine, diagnostics evaluation.

Respond to this report

Responses (2)

Author Response

20 Jul 2022

Dina Naser, Virology, Central Laboratory, Khartoum, Sudan

Dear Ralph Huits,

Major comment:
The selected mothers had received the YFV vaccine within 9 months of delivery. They were not showing any symptoms of YVF before they got the vaccines; however, their infants developed symptoms of fever, diarrhea, jaundice, vomiting, and/or skin rashes after one week from their mother received the vaccines.

Transmission to infants was confirmed through that their mothers get vaccinated week before developing symptoms and also through the detected YFV RNA in milk specimens from these same mothers during the infant’s appeared symptoms.

Minor comments:

Result:

Do ‘Right’/ ‘Left’ column headings refer to the right/left mamma?

Yes, milk samples collected from both breasts in order to get the most excreted YFV in milk and also to study if there is any relation or correlation between breast side and YFV shedding in milk.

*Other reviewer edits are done in the new submitted version.*

View more View less

Competing Interests

No competing interest.

Back to all reports

Reviewer Report

9 Views

22 Mar 2022 | for Version 2

Leo G Visser, Department of Infectious Diseases, Leiden Medical University Center, Leiden, The Netherlands

9 Views Cite this report Responses(0)

Approved

The authors have addressed the concerns raised in the peer review report appropriately.

Competing Interests

No competing interests were disclosed.

Reviewer Expertise

Vaccine immunology, alternative vaccination routes, yellow fever vaccine, rabies vaccine, mRNA 1273

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.

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Reviewer Report

24 Views

07 Feb 2022 | for Version 1

Leo G Visser, Department of Infectious Diseases, Leiden Medical University Center, Leiden, The Netherlands

24 Views Cite this report Responses(0)

Approved With Reservations

Is the work clearly and accurately presented and does it cite the current literature?

Yes
Is the study design appropriate and is the work technically sound?

Partly
Are sufficient details of methods and analysis provided to allow replication by others?

Yes
If applicable, is the statistical analysis and its interpretation appropriate?

Not applicable
Are all the source data underlying the results available to ensure full reproducibility?

No source data required
Are the conclusions drawn adequately supported by the results?

Partly

References

Competing Interests

No competing interests were disclosed.

Reviewer Expertise

Vaccine immunology, alternative vaccination routes, yellow fever vaccine, rabies vaccine, mRNA 1273

Respond to this report

Responses (0)

Alongside their report, reviewers assign a status to the article:

Approved - the paper is scientifically sound in its current form and only minor, if any, improvements are suggested

Approved with reservations - A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit.

Not approved - fundamental flaws in the paper seriously undermine the findings and conclusions

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[8] 8. Couto A, Salomão M, Schermann M, et al.: Transmission of yellow fever vaccine virus through breast-feeding-Brazil, 2009. Morb. Mortal. Wkly Rep. 2010; 59(5): 130–132.

[9] 9. Traiber C, Coelho-Amaral P, Ritter VRF, et al.: Infant meningoencephalitis caused by yellow fever vaccine virus transmitted via breastmilk. J. Pediatr. 2011; 87(3): 269–272.

[10] 10. Kuhn S, Twele-Montecinos L, MacDonald J, et al.: Case report: probable transmission of vaccine strain of yellow fever virus to an infant via breast milk. CMAJ. 2011; 183(4): E243–E245. PubMed Abstract | Publisher Full Text

[11] 11. Barthel A, Gourinat A-C, Cazorla C, et al.: Breast milk as a possible route of vertical transmission of dengue virus? Clin. Infect. Dis. 2013; 57(3): 415–417. PubMed Abstract | Publisher Full Text

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[13] 13. Colt S, Garcia-Casal MN, Peña-Rosas JP, et al.: Transmission of Zika virus through breast milk and other breastfeeding-related bodily-fluids: A systematic review. PLoS Negl. Trop. Dis. 2017; 11(4): e0005528. PubMed Abstract | Publisher Full Text

[14] 14. Hinckley AF, O’Leary DR, Hayes EB: Transmission of West Nile virus through human breast milk seems to be rare. Pediatrics. 2007; 119(3): e666–e671. PubMed Abstract | Publisher Full Text

[15] 15. Bashir R, Hassan T, Abdelrahman N, et al.: Transmission of yellow fever vaccine virus from breast feeding mothers to their infants: reporting of yellow fever virus (YFV) RNA detection in milk specimens. figshare. Dataset. 2021. Publisher Full Text

[16] 16. Staples JE, Gershman M, Fischer M: Yellow fever vaccine: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm. Rep. 2010; 59(RR-7): 1–27. PubMed Abstract

[17] 17. Lecomte E, Laureys G, Verbeke F, et al.. A clinician’s perspective on yellow fever vaccine-associated neurotropic disease.J. Travel Med.2020 Oct; 27(7): taaa 172. Publisher Full Text PubMed Abstract |

[18] 18. Centers for Disease Control and Prevention CDC: Transmission of yellow fever vaccine virus through breast-feeding - Brazil, 2009. MMWR Morb. Mortal. Wkly. Rep. 2010; 59(5): 130–132. PubMed Abstract

[19] 19. Fernandes EG, Nogueira JS, Porto VBG, et al.: The search for yellow fever virus vaccine in breast milk of inadvertently vaccinated women in Brazil. Rev. Inst. Med. Trop. Sao Paulo. 2020; 62: e33. PubMed Abstract | Publisher Full Text

[20] 20. Ribeiro AF, Brasil LMCR, Prada RM, et al.: Detection of Wild-type Yellow Fever Virus in Breast Milk. Pediatr. Infect. Dis. J. 2020; 39(1): 68–69. PubMed Abstract | Publisher Full Text

[21] 21. Witkowska-Zimny M, Kaminska-El-Hassan E: Cells of human breast milk.Cell. Mol. Biol. Lett.2017 Dec; 22(1): 1–1. Publisher Full Text

Transmission of yellow fever vaccine virus from breast feeding mothers to their infants: reporting of yellow fever virus (YFV) RNA detection in milk specimens

Abstract

Background

Methods

Results

Conclusions

Keywords

Revised Amendments from Version 3

Introduction

Methods

Ethical considerations

Study design and population

Sample collection

Serology

RNA extraction

Real-time polymerase chain reaction (PCR)

Statistical methods

Results

Figure 1. Participation per each phase of the study.

Results of the first collection

Figure 2. Result of anti-YFV IgM using IFA technique.

Table 1. Results of serological and molecular detection of YFV in milk and serum specimens.

Figure 3. Real time polymerase chain reaction (PCR) result for yellow fever virus (YFV) positive milk specimens.

Results of the second collection

Results of the third collection

Results of the fourth collection

Figure 4. Result of yellow fever virus (YFV) detection among different collection dates.

Discussion

Conclusion

Data availability

Underlying data

References

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