Emerging pneumococcal serotypes in Iraq: scope for improved vaccine development

Pneumococcal disease is a global public health concern as it affects the young, aged and the immunocompromised. The development of pneumococcal vaccines and their incorporation in the immunization programs has helped to reduce the global burden of disease. However, serotype replacement and the emergence of non-vaccine serotypes as well as the persistence of a few vaccine serotypes underscores the need for development of new and effective vaccines against such pneumococcal serotypes. In the Middle East, places of religious mass gatherings are a hotspot for disease transmission in addition to the global risk factors. Therefore, the periodic surveillance of pneumococcal serotypes circulating in the region to determine the effectiveness of existing prevention strategies and develop improved vaccines is warranted. Currently, there is a lack of serotype prevalence data for Iraq due to inadequate surveillance in the region. Thus, this review aims to determine the pneumococcal serotypes circulating in Iraq which may help in the development and introduction of improved pneumococcal vaccines in the country.


Introduction
Streptococcus pneumoniae, the causative agent of pneumococcal disease, is responsible for devastating morbidity and mortality among children <5 years of age, adolescents, adults >60 years of age, the immunocompromised population, patients with chronic diseases, and smokers. 1,2It is a commensal microbe that normally colonizes the upper respiratory mucosa of humans, which in turn facilitates its transmission. 3However, several bacterial and host factors promote pathogen invasion into sterile body sites, thereby causing severe invasive pneumococcal disease (IPD) manifestations, such as septicemia, meningitis, and bacteremic pneumonia. 3,4As a public health prevention strategy, the World Health Organization (WHO) has recommended the global inclusion of pneumococcal conjugate vaccines (PCVs) into routine infant immunization programs. 57][8] In addition, the pneumococcal polysaccharide vaccine (PPSV) was developed to prevent IPD among the elderly (≥65 years) and high-risk populations (≥2 years). 9[12][13] Due to the lack of adequate surveillance in the region, limited serotype prevalence data are available for Iraq.This review aims to revise and shed light on the S. pneumoniae serotypes circulating in the country.All systematic reviews used in this manuscript were found to be reliable in terms of heterogeneity and analysis.We hope that this review will aid readers (researchers and policymakers) in making informed decisions regarding the development and introduction of improved pneumococcal vaccines.

S. pneumoniae serotypes
Pneumococci possess several virulence factors, of which the polysaccharide capsule is the most important, as it is an essential armor against phagocytosis and aids colonization by overcoming its mucus-mediated clearance. 14,15The capsule is also the target antigen for the development of multivalent vaccines against this pathogen.Pneumococcal serotypes are differentiated based on antigenic differences and the chemical composition of these capsular polysaccharides. 14A serogroup includes serotypes that have common serological properties (i.e., cross-reactive antibodies). 16ile most pneumococcal capsules are generally anionic, the capsule of serotype 1 exists as a zwitterion and those of serotypes 7A, 7F, 14, 33A, 33F, and 37 have been reported to be uncharged. 16The capsule of serotype 14 is less soluble than other pneumococcal polysaccharide capsules. 16The capsule strands are normally linked to the bacterial surface via covalent linkages to the peptidoglycan, except in the case of serotype 3, where noncovalent interactions with phosphatidylglycerol have been reported. 17It has been suggested that the release of the capsular polysaccharide of serotype 3 strains reduces antibody-mediated protection and is responsible for the reduced efficacy of the currently available PCV against serotype 3. 18 Serotype distribution varies temporally and geographically and is also influenced by age, the presence of antimicrobial resistance genes, as well as disease syndrome and severity. 5The establishment of this commensal nasopharyngeal flora occurs within the first year of birth. 19Nasopharyngeal carriage determines disease development as well as pathogen dissemination.Infants and young children have higher carriage rates (27-85%) than adults (~10%). 5,14It has been reported that a carriage rate of 30-40% is maintained till the age of 9 years, progressively declining thereafter. 14In fact, the low carriage rates among adults indicates immunological protection upon previous exposure. 14,19Variations in carriage rates have been noted to depend upon the local epidemiology, with higher rates noted in socioeconomically weaker countries and in impoverished communities with low vaccination rates. 5,141][22] Young children (<5 years) and

REVISED Amendments from Version 1
In this revised version, we have responded to all reviewer comments and addressed them accordingly in the manuscript.We have revised the introduction and conclusions sections based on reviewer comments.Available IPD incidence for Saudi Arabia has been added.We have assessed the quality of SLRs/meta-analyses used in this manuscript and added a relevant statement in the Introduction.Two tables have been introduced: one describing the colonization or invasive potential of S. pneumoniae serotypes and the other providing an age-wise stratification and antibiotic resistance profile of S. pneumoniae isolates in the Eastern Mediterranean Region, as suggested by the reviewer.
8][59][60] Although pneumococcal vaccines have had a tremendous impact on the global pneumococcal disease burden, serotype replacement (i.e., the replacement of the vaccine serotypes [VTs] with nonvaccine serotypes) has slightly dulled the overall benefits of immunization. 11terations in the serotype prevalence among pneumococcal populations can originate from both serotype replacement as well as serotype (capsular) switching. 61Serotype replacement refers to the expansion of NVTs within the population. 62,63n the other hand, serotype switching, or capsular switching, is the change in a serotype from a single clone that occurs due to alterations in the cps locus which is responsible for capsular polysaccharide synthesis. 61These 2 events are not mutually exclusive, as capsular switch variants often expand within the population. 61,62obal pneumococcal serotype prevalence In the period preceding worldwide PCV introduction, the most commonly circulating pneumococcal serotypes in children (<5 years) were reported to be 1, 5, 6A, 6B, 14, 19F, and 23F, which accounted for 58-66% of global IPD cases. 21During this period, PCV7-related serotypes were responsible for 49-82% of global childhood IPD episodes. 21pon PCV7 implementation, the percentage of IPD cases caused by PCV7 serotypes reduced to approximately 14.8% and to 12.5% after the introduction of the higher-valent PCVs (i.e., PCV10/13). 64,65The PCV10-specific serotypes 1, 5, and 7F accounted for 16.3% of overall childhood IPD cases in regions where PCV7 had been introduced, while the figure was 9.2% in post-PCV10/13 implementation settings. 64Following the introduction of PCV7 and PCV10/13, the most common PCV13 serotypes were 19A, 3, and 6A. 45,64Serotype 19A was the most prevalent (21.8% cases) among pediatric IPD cases in the post-PCV7 period, and was responsible for 14.2% of incidents in regions with higher-valent vaccine introduction. 64The global increase in the prevalence of serotype 19A in the PCV13 period is a cause of concern, as it indicates reduced vaccine efficacy against this serotype. 45Furthermore, this serotype is also globally associated with high multidrug resistance (MDR) potential.Wantuch and Avci also highlight PCV13's reduced effectiveness against serotype 3 prevalence, which has remained nearly constant in the pre- (1999-2000) and post-PCV (2010-2011) periods. 45obally, about 29.4% and 42% of childhood IPD cases were caused by non-PCV13 serotypes in post-PCV7 and post-PCV10/13 administration settings, respectively.Serotype 22F was the most prevalent (5% of childhood IPD episodes) in regions where PCV10/13 had been introduced, followed by 12F, 33F, 24F, and 15C (~4% episodes each).Serotypes 15B, 23B, 10A, and 38 were responsible for 3.4-3.7% of cases globally.However, several variations in the prevalence of these serotypes were observed across different regions.In several regions, except in the EMR, serotypes 22F, 12F, and 33F were responsible for 4-16% of childhood IPD cases.Serotype 24F was prevalent in the Western Pacific region and Europe (but not North America).Serotype 38 was more prevalent in North America and 12F, 15C, and 10A in Europe. 64n Japan, a nationwide surveillance study was conducted between 2012 and 2014 among pediatric (2 months-16 years) patients that revealed the emergence of IPD due to NVTs 24F and 15A post-approval of PCV13 use in routine vaccination. 66Ubukata et al. found that the prevalence of 9 (10A, 12F, 15A, 15B, 15C, 22F, 24F, 33F, and 35B) and 5 serotypes (12F, 15C, 22F, 23A, and 35B) increased significantly among children and adults, respectively, during the PCV13 period.Notably, a rapid increase was observed in 15A and 35B. 67The NVT 24F was recently reported to be a cause of concurrent bacteremia among 22-month-old twins who had been fully vaccinated with PCV13, with the last dose administered 6 months prior to hospitalization. 68This serotype also showed a high invasive potential (pneumococcal meningitis) post-PCV13 implementation in France in the pediatric population along with serotype 12F. 69,70eumococcal serotype prevalence in the Eastern Mediterranean Region The EMR has a substantial burden of lower respiratory tract infections, with pneumococci contributing maximally to the mortality rate (16.6 per 100,000). 71In 2015, this region reported 37,100 pneumococcal deaths and 968,000 pneumococcal disease cases. 7High-income countries within the region have introduced PCV into their National Immunization Programs (NIPs), and several low-income countries have received support from Gavi, the Vaccine Alliance, for the same. 71Several middle-income countries have now introduced PCV, except for a few countries such as Iran, Jordan and  The Gulf countries of the Middle East exhibit a high pneumococcal disease burden, with risk factors similar to those existing globally, such as age-related risks, chronic disease-related risks, as well as risks arising due to immunodeficiencies, smoking, and alcoholism. 72,735][76][77] However, inadequate surveillance as well as inconsistent reporting methods are associated with an underestimation of pneumococcal diseases burden in the Gulf countries. 78Thus, the active surveillance of pneumococcal serotypes prevalent within this region would help determine the effectiveness of the adopted immunization strategies and aid in developing novel measures to control disease transmission and outbreaks.Currently, the EMR has a vaccination coverage of 52% for 3 doses of PCV. 791][82]  Recently, a systematic review and meta-analysis of published reports between 2010 and 2017 showed that the overall prevalence of invasive S. pneumoniae infections is very low (2.5%) among Iranian children. 83However, as the included studies covered only 3 geographical regions within the country, this study was not fully representative of the whole population and could not entirely estimate the overall S. pneumoniae prevalence.Among children (<5 years) in Tehran, serotype 23F was reported to be the most invasive circulating serotype, followed by 19F, 19A, and 9V.Serotype 19A was significantly associated with penicillin resistance. 84other systematic literature review on pneumococcal serotype distribution conducted among clinical and carrier Iranian patients between January 2000 and August 2019 revealed that 23F was the most commonly circulating serotype in Iran and was associated with IPD.Other serotypes that caused IPD included 19F, 19A, 6A/B, 9V, and 11A.Among carrier patients, 6A/B, 19F, 14, 17F, and 20 were the most frequent. 85study conducted between February 2015 and September 2015 and between July 2018 and March 2019 collected approximately 40 samples during each period from patients (1 month to 72 years of age) in Tehran. 86About 38 of these samples were derived from invasive infections, of which 42% occurred in children ≤5 years.The pneumococcal serotypes in the samples were determined to be 23F, 14, 3, 19F, 19A, 6A, 6B, 9V, and 18C, of which the first 5 were the most common (in decreasing order).This is consistent with serotype prevalence data for other Asian countries. 87,88he common serotypes isolated from invasive infections were 23F, 19A, and 14, while 3, 19F, and 23F were commonly associated with noninvasive disease.Among pediatric patients ≤5 years, the most prominent serotypes were 19A, 3, 23F, and 14, while 23F was predominant in adults ≥64 years.In the former age group, serotype 19A was observed in 35.2% of IPD cases, while serotypes 3, 23F, and 14 were predominantly non-IPD related.Overall, serotype 23F was frequently associated with penicillin resistance and was also predominant among MDR strains.A significant rise in serotype 19A MDR isolates was noticed among invasive infections in the second period of sample collection, possibly due to antibiotic selection pressure. 86aq Iraq incorporated the use of PCV into the NIP in 2017.However, there are insufficient serotype surveillance data for Iraq.Most publications on S. pneumoniae in this region focus on its antimicrobial resistance, but do not identify the serotype of the isolate.Between June 2018 and May 2020, 41.6% of patients were confirmed to have pneumococcal meningitis in Iraq based on cerebrospinal fluid samples. 89The age of patients ranged from 1 to 40 years, with a majority (83.7%) being under 5 years and 58.4% being less than a year old.The overall annual incidence rate (IR) of laboratory-confirmed pneumococcal meningitis in Iraq was 0.62/100,000, with a maximum IR of 1.56 in Karbala (site of Arba'een pilgrimage), 0.65 in Karkh, 0.58 in Al-Rusafa, 0.3 in Kirkuk, and a minimum of 0.09 in Maysan.However, as all Iraqi governorates were not covered in this study, the overall incidence rate for pneumococcal meningitis was likely underestimated.In a recent report, a nonvaccine S. pneumoniae serotype, 33C, was isolated from a hospitalized child with nephrotic syndrome and sepsis, which can be fatal. 90

Kuwait
2][93] The 7-valent PCV was introduced to the pediatric population in 2007 and was replaced with the higher-valent (PCV13) formulation in 2010. 93In the period following PCV7's introduction (2006-2011), a majority (46%) of clinical pneumococcal isolates were derived from the adult population >50 years, where 27% of cases were found to be invasive.Although a lower percentage (23%) of isolates were obtained from pediatric (≤5 years) samples, IPD was responsible for nearly half (49%) of the cases in this age group. 91The common serotypes circulating among children (≤5 years) during this period were 19F, 19A, 6A, 8, and 15B (invasive) and 19F and 23F (noninvasive). 91Serotypes 14, 3, 1, 19F, and 8 were associated with invasive disease and 19F, 23F, 6B, 14, and 19A with noninvasive events among the adult population >50 years. 91In comparison to the pre-PCV (10.33 isolates/year) and post-PCV7 (7.75 isolates/year) periods, PCV7-related serotypes showed a greater decline after PCV13 introduction, falling to 1.4 isolates/year. 78An increased incidence of cases due to non-PCV7 serotypes 1, 6A, and 3 (which are included in PCV13) was reported post-PCV7 vaccine introduction. 91After the introduction of the 13-valent vaccine, the 6 additional serotypes included in PCV13 showed a reduced frequency of occurrence (3.12 isolates/year) as compared to the pre-PCV (4 isolates/year) and post-PCV7 (7.5 isolates/year) periods, while the nonvaccine serotypes increased (13.25 isolates/year post-PCV7 and 11.52 isolates/year post-PCV13 introduction as compared to 6.33 isolates/year in the pre-PCV phase). 78

Lebanon
In The NVT 24F has been reported to be an emerging serotype among patients with IPD (mostly [87.5%] <6 years of age with unknown pneumococcal vaccination status) in Lebanon, with 4 cases noted in 2019. 95The genome sequencing of this serotype, isolated from samples collected between 2013 and 2019, showed that it is highly virulent and antimicrobial resistant. 95The prevalence of this NVT among IPD cases in children has also been reported in the European and Western Pacific regions. 64,68,70,96,97rocco During a surveillance study conducted between September 2007 and August 2008 in Casablanca, serotypes 19F, 14, 23F, 6B, and 19A were found to be prevalent among pediatric (<5 years) IPD patients. 82Recently, a report was published on early neonatal respiratory distress, revealing meningitis caused by serotype 17F via vertical transmission. 98udi Arabia PCV7 was incorporated into the Saudi Arabian NIP in 2008 and was replaced with the 13-valent vaccine in 2010.99 A multicenter, prospective study conducted between June 2007 and January 2009 estimated the incidence of confirmed IPD cases to be 2.5À21.6 per 100,000 children <5 years.100 Between 2005 and 2010, serotypes 23F, 19F, 6B, 5, and 1 were commonly associated with invasive episodes among children <5 years.99 This period showed a notable decline in the PCV7 serotype 18C and a significant rise in the PCV13 serotype 19A.99 About 66% and 62% of isolates were reported to be penicillin and erythromycin resistant, respectively. In this study, all pneumococcal isolates were found to be resistant to cotrimoxazole, while 77% and 36% were observed to be erythromycin and penicillin resistant, respectively.Penicillin resistance was higher among serotypes 23F, 6B, and 19F.101 In the post-PCV13 introduction phase (January 2012 to December 2014), serotypes commonly isolated from the Eastern province of Saudi Arabia included 11A, 19A, 17F, 23F, 3 and 19F.102 The previously rare but most prevalent serotype in this study, 11A (part of PPSV23), exhibited maximum penicillin resistance.Overall, 67.9% of isolates were resistant to both penicillin and macrolides, 17% to only penicillin and 5.6% to only macrolides.102 These reports indicate that there is widespread drug resistance among pneumococcal isolates in Saudi Arabia.Of the pneumococcal isolates collected from 24 Saudi Arabian hospitals between January and December 2009, 33% were resistant to penicillin G, 26% to erythromycin, and 11% to ceftriaxone.103

Conclusions
The reduction in the occurrence of vaccine-type serotypes since the introduction of PCVs points towards the might of vaccines in combating deadly infectious diseases.However, growing antibiotic resistance, serotype switching and replacement, and the persistence of a few vaccine serotypes (especially serotypes 3 and 19A) indicates that both vaccine-type and nonvaccine-type pneumococcal serotypes still remain a global public health concern.Thus, there is an ever-increasing need to combat IPD via effective, new-generation vaccines that utilize effective immune mechanisms, especially in the case of serotype 3, which can evade the immune system.Limited serotype prevalence data are available for Iraq due to lack of facilities for laboratory studies.In addition, issues such as vaccine inaccessibility in the public sector, war and conflict situation, displacement camps and climate change characterized by high temperature, dust storms, drought and increased desertification are additional challenges for a successful pneumococcal vaccination program in the country.Pneumococcal serotypes in Iraq are likely to be similar to those circulating in the neighboring countries due to similarities including ecological conditions and cultural practices like mass gatherings during worship.However, serotype replacement and capsule switching are regulated by selection pressure unique to the population.Thus, in Iraq and its neighboring countries in the EMR, improving surveillance would help provide the essential disease burden data required for refining vaccination strategies and improving outcomes.The active surveillance of NVT 33C, recently isolated from Iraqi children with nephrotic syndrome and sepsis, is essential to understand the degree of spread of the pathogen among Iraqi communities.In the PCV13 era, the emergence of serotype 24F in many regions of the world as one with maximum invasive potential and multidrug resistance warrants its periodic surveillance, as well as its inclusion in the next generation of pneumococcal vaccines.Improved polyvalency of vaccines, such as those under development by Inventprise and Vaxcyte, would help combat nonvaccine serotypes.Such an expanded coverage by the newer generation of vaccines is theoretically expected to reduce IPD cases caused by emerging non-PCV13 serotypes.In conjunction, continuous studies on molecular epidemiology of the pathogen within the EMR region would also help monitor antibiotic resistance patterns.We hope that this review guides policymakers and researchers to make informed decisions pertaining to the development and introduction of improved pneumococcal vaccines in Iraq.
since it is a place of mass religious gatherings and pneumococcus is widely known for its horizontal gene transfer and global spread of resistant clones.In my opinion the authors can summarize the data and present it in a way that makes it easily comprehensible for readers rather than simply presenting the data on serotype prevalence.Below are my specific comments.Most of the data presented in this review is drawn from systematic reviews.Since the inferences drawn in the review rely on these systematic reviews, it is important to assess the QC of these reviews such as clinical heterogeneity, statistical heterogeneity as well as models used for meta analysis.In some cases, the authors refer to systematic reviews from very few geographical regions of a country -e.g.Iran.How reliable are these studies?The reliability of the data presented is heavily dependent on the QC of these meta analyses.Therefore the authors need to ensure that they only present data from robust systematic reviews. 1.
Section on pneumococcal serotypes -I suggest that the authors tabulate the pneumococcal serotypes associated with colonization vs. invasive disease along with the supporting references.

2.
Many times the authors list some serotypes as frequently associated with carriage and IPD.This does not make sense.For e.g.page 6, under data from Iran, 19F is classified into both IPD and carrier populations.
Similarly, serotype 23F is listed under both carriage and IPD.

3.
For the data on countries from EMR region, age-wise stratification of serotype prevalence and correlation with antibiotic resistance profile is needed.

4.
The authors need to refrain from claiming that they can draw inference for Iraq from neighboring countries since although regions are located geographically closer, serotype replacement and capsule switching are regulated by selection pressure unique to the population.Even in this review there are unique serotypes associated with Iraq such as NVT 33C that is not found elsewhere in the region.

5.
Is 5.The authors need to refrain from claiming that they can draw inference for Iraq from neighboring countries since although regions are located geographically closer, serotype replacement and capsule switching are regulated by selection pressure unique to the population.Even in this review there are unique serotypes associated with Iraq such as NVT 33C that is not found elsewhere in the region.
Author Response: The authors would like to thank the reviewer for this suggestion.We have removed this statement from the abstract and from the Introduction section (Page 3, paragraph 2) and modified the paragraph to ensure readability.
ecological conditions, cultural practices (like mass gatherings during worship).
Is burden data available for any of Iraq's neighbors (Iran, Kuwait, Saudi Arabia etc.).If so, how does that compare with Iraq's IPD incidence of 0.62/100,000? 2.
Minor issue: The opening statement in the Introduction could be rewritten as follows; "....for devastating morbidity and mortality among children below five years of age, adolescents, adults above 60 years of age, the immunocompromised population...". the available literature, the prevalence of invasive S. pneumoniae infections was found to be low (2.5%) among children in Iran (Avarvand et al., 2021).This data is already available in the section on Iran (Page 12).In Saudi Arabia, the incidence of confirmed IPD cases was estimated to be 2.5−21.6 per 100,000 children (<5years) (Almazrou et al., 2016).This has now been added to the section on Saudi Arabia (Page 14) as: "A multicenter, prospective study conducted between June 2007 and January 2009 estimated the incidence of confirmed IPD cases to be 2.5−21.6 per 100,000 children <5 years."Its reference has been added to the end of the reference list as per journal guidelines.Further we have also added a statement to Page 8: "However, inadequate surveillance as well as inconsistent reporting methods are associated with an underestimation of pneumococcal diseases burden in the Gulf countries (Mokaddas et  The benefits of publishing with F1000Research:

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Your article is published within days, with no editorial bias • You can publish traditional articles, null/negative results, case reports, data notes and more • The peer review process is transparent and collaborative • Your article is indexed in PubMed after passing peer review • Dedicated customer support at every stage • For pre-submission enquiries, contact research@f1000.com the topic of the review discussed comprehensively in the context of the current literature?Yes Are all factual statements correct and adequately supported by citations?Yes Is the review written in accessible language?Yes Are the conclusions drawn appropriate in the context of the current research literature?Partly Competing Interests: No competing interests were disclosed.Reviewer Expertise: Epidemiology of infectious diseasesI 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.

Table
. Colonization or invasive potential of S. pneumoniae serotypes.

Table 3 .
Age-wise stratification and antibiotic resistance among S. pneumoniae isolates in the Eastern Mediterranean Region.
Table 3 provides an age-wise stratification of serotype prevalence in the EMR and correlation with antibiotic resistance (where available).Pneumococcal vaccines have not yet been included in the NIP of Iran and are only recommended for high-risk groups.

the topic of the review discussed comprehensively in the context of the current literature? Yes Are all factual statements correct and adequately supported by citations? Yes Is the review written in accessible language? Yes Are the conclusions drawn appropriate in the context of the current research literature? Yes Competing Interests:
No competing interests were disclosed.

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.
Homogenous data: In Africa, ten serotypes had an ICC (Intraclass correlation) <0.2, thus the meta-estimates for these ten serotypes are particularly sensitive to the addition or removal of serotype data in this region.Asia and LAC also had a large number of serotypes with ICC<0.2 (six and five serotypes, respectively).contrast, in Oceania, only serotype 14 had an ICC<0.2,indicating relative homogeneity in the reported serotype proportion data for this region.
Mitigation: Marginal random-effects meta-analysis Interpretation in terms of significant heterogenous (Yes/No): No heterogeneity with 160 studies data so considered Study: Balsells et al., 2017 Number of studies included: 68 studies I 2 /Heterogeneity: Datasets were heterogenous Mitigation: Random effects model (DerSimonian-Laird method).Heterogeneity was addressed by analyzing the most comparable data and case definitions.Analysis was stratified by PCV vaccine formulation and used data for children of the same age (<5 years) whenever possible.Sensitivity analysis was performed.

Interpretation in terms of significant heterogenous (Yes/No): Though
The authors would like to thank the reviewer for this suggestion.We have created Table1(Page 5) which provides the "Colonization or invasive potential of S. pneumoniae serotypes".As per journal guidelines all tables have been shared in a separate document.Thank you for your comment.Both serotypes 19F and 23F cause invasive disease but are also common in carriage(Sandgren et al., 2004).This can be clearly visualized in the newly created tables 1 and 3 of the revised manuscript.The ability of pneumococcal serotypes to colonize or cause invasive disease may be influenced by both host-derived as well pathogen-derived factors.As per published literature, both serotypes 19F and 23F have a low invasive potential and are primarily found in carriers(Burgess et al.,  2008).These serotypes are known to be associated with an impaired antibody response following invasive pneumococcal disease(Littorin et al., 2018; Soininen et al., 2001).Further, in addition to the capsular serotype, the clonal type may also determine the disease causative potential of pneumococcal serotypes as published by Sandgren et al. (2004) who reported that clones belonging to the same serotype showed different abilities to cause invasive disease.4.For the data on countries from EMR region, age-wise stratification of serotype prevalence and correlation with antibiotic resistance profile is needed.Author Response: Thank you for your suggestion.We have incorporated Table3into the manuscript (Pages 9−11) which provides an "Age-wise stratification and antibiotic resistance among S. pneumoniae isolates in the Eastern Mediterranean Region".As per journal guidelines all tables have been shared in a separate document.
al., 2018)".3. Minor issue: The opening statement in the Introduction could be rewritten as follows; "....for devastating morbidity and mortality among children below five years of age, adolescents, adults above 60 years of age, the immunocompromised population...".Author Response: Thank you for your suggestion.The opening statement in the Introduction (Page 2) has now been modified as follows: "Streptococcus pneumoniae, the causative agent of pneumococcal disease, is responsible for devastating morbidity and mortality among children <5 years of age, adolescents, adults >60 years of age, the immunocompromised population, patients with chronic diseases, and smokers." Competing Interests: None to declare.