On 2015 Dec 08, S. Celeste Morley commented:

Thank you very much for your interest in and comment upon our work. The safety and efficacy of PCV in preventing and reducing the incidence of invasive pneumococcal disease is unquestioned and unequivocally supported by all literature. The mechanisms by which PCV protects are multifactorial. PCV generates an immune response that protects against invasive disease, if not colonization. We did not address incidence of IPD in this study. PCV also results in decreased carriage prevalence of the disease-causing serotypes covered by the vaccine, and thus shifts serotype prevalence without necessarily altering overall carriage prevalence. Our study simply reported overall carriage prevalence and the antibiotic susceptibility profiles of carriage isolates; we did not report serotypes. Our results finding that overall likelihood of colonization with any pneumococcal serotype is not affected by PCV is in line with other larger studies (e.g. Zuccotti et al Vaccine. 2014 Jan 23;32(5):527-34. Zuccotti G, 2014) Thus, our study is not in conflict with any of the studies referenced above, which clearly show a decrease in colonization with vaccine-covered serotypes.

On 2015 Dec 07, Manoochehr Karami commented:

Manoochehr Karami, PhD, Research Center for Health Sciences and Department of Epidemiology, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran.

In an interesting study published recently, Julie Y. Zhou et al.(1) highlighted the prevalence of nasopharyngeal pneumococcal colonization among children in the greater St. Louis hospital. Authors have stated "pneumococcal conjugate vaccine (PCV) did not alter prevalence" of nasopharyngeal carriage. World Health Organization indicated that after PCV introduction, both targeted and non-targeted vaccination population were affected by direct and indirect effects of PCV immunization(2). Moreover, published studies (3-7) supported the changes of epidemiological profile of Streptococcus pneumonia related diseases transmission and nasopharyngeal carriage even among those individuals who were not immunized against Streptococcus pneumonia. Accordingly, it seems Zhou JY et al. interpretations based on their findings is in question and might be affected because of potential selection bias while enrolled participants. Rational for such selection bias is the catchment area of St. Louis hospital and potential differences between study participants and non-participants. Although they have excluded some patients, however this strategy does not guarantee the representativeness of their own work. Generally speaking, better explanation for Zhou et al findings is selection bias. In conclusion, lack of generalizability of this study findings should be considered by policy makers and interested readers.   References: 1. Zhou JY, Isaacson-Schmid M, Utterson EC, et al. Prevalence of nasopharyngeal pneumococcal colonization in children and antimicrobial susceptibility profiles of carriage isolates. International Journal of Infectious Diseases;39:50-52. 2. World Health Organization. Measuring impact of Streptococcus pneumoniae and Haemophilus influenzae type b conjugate vaccination. WHO Press, Geneva, Switzerland, 2012. 3. World Health Organization.Pneumococcal vaccines WHO position paper – 2012.Wkly Epidemiol Rec. 2012;87:129-244. . 4. Lehmann D, Willis J. The changing epidemiology of invasive pneumococcal disease in aboriginal and non-aboriginal western Australians from 1997 through 2007 and emergence of nonvaccine serotypes. Clinical Infectious Diseases. 2010, 50(11):1477–1486. 5. Pilishvili T, Lexau C. Sustained reductions in invasive pneumococcal disease in the era of conjugate vaccine. The Journal of Infectious Diseases, 2010, 201(1):32–41. 6. Davis S, Deloria-Knoll M, Kassa H, O’Brien K. Impact of pneumococcal conjugate vaccines on nasopharyngeal carriage and invasive disease among unvaccinated people: Review of evidence on indirect effects. Vaccine.2014;32:133-145. 7. Karami M, Alikhani MY. Serotype Replacement and Nasopharyngeal Carriage Due to the Introduction of New Pneumococcal Conjugate Vaccine to National Routine Immunization. Jundishapur Journal of Microbiology 2015;8.

On 2015 Dec 07, Manoochehr Karami commented:

Manoochehr Karami, PhD, Research Center for Health Sciences and Department of Epidemiology, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran.

In an interesting study published recently, Julie Y. Zhou et al.(1) highlighted the prevalence of nasopharyngeal pneumococcal colonization among children in the greater St. Louis hospital. Authors have stated "pneumococcal conjugate vaccine (PCV) did not alter prevalence" of nasopharyngeal carriage. World Health Organization indicated that after PCV introduction, both targeted and non-targeted vaccination population were affected by direct and indirect effects of PCV immunization(2). Moreover, published studies (3-7) supported the changes of epidemiological profile of Streptococcus pneumonia related diseases transmission and nasopharyngeal carriage even among those individuals who were not immunized against Streptococcus pneumonia. Accordingly, it seems Zhou JY et al. interpretations based on their findings is in question and might be affected because of potential selection bias while enrolled participants. Rational for such selection bias is the catchment area of St. Louis hospital and potential differences between study participants and non-participants. Although they have excluded some patients, however this strategy does not guarantee the representativeness of their own work. Generally speaking, better explanation for Zhou et al findings is selection bias. In conclusion, lack of generalizability of this study findings should be considered by policy makers and interested readers.   References: 1. Zhou JY, Isaacson-Schmid M, Utterson EC, et al. Prevalence of nasopharyngeal pneumococcal colonization in children and antimicrobial susceptibility profiles of carriage isolates. International Journal of Infectious Diseases;39:50-52. 2. World Health Organization. Measuring impact of Streptococcus pneumoniae and Haemophilus influenzae type b conjugate vaccination. WHO Press, Geneva, Switzerland, 2012. 3. World Health Organization.Pneumococcal vaccines WHO position paper – 2012.Wkly Epidemiol Rec. 2012;87:129-244. . 4. Lehmann D, Willis J. The changing epidemiology of invasive pneumococcal disease in aboriginal and non-aboriginal western Australians from 1997 through 2007 and emergence of nonvaccine serotypes. Clinical Infectious Diseases. 2010, 50(11):1477–1486. 5. Pilishvili T, Lexau C. Sustained reductions in invasive pneumococcal disease in the era of conjugate vaccine. The Journal of Infectious Diseases, 2010, 201(1):32–41. 6. Davis S, Deloria-Knoll M, Kassa H, O’Brien K. Impact of pneumococcal conjugate vaccines on nasopharyngeal carriage and invasive disease among unvaccinated people: Review of evidence on indirect effects. Vaccine.2014;32:133-145. 7. Karami M, Alikhani MY. Serotype Replacement and Nasopharyngeal Carriage Due to the Introduction of New Pneumococcal Conjugate Vaccine to National Routine Immunization. Jundishapur Journal of Microbiology 2015;8.