The impact of pneumococcal conjugate vaccines on serotype prevalence, proportion, and antibiotic susceptibility of streptococcus pneumoniae among children 0 to 84 months from 2004 through 2023 at Boston Medical Center
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Abstract
INTRODUCTION: The impact of pneumococcal conjugate vaccines (PCV) on nasopharyngeal (NP) carriage provides insight into the potential for herd effect, serotypes that may emerge in ‘replacement’ disease, as well as likelihood of cross-protection against nonvaccine serotypes.
METHODS: We analyzed NP colonization from 8 studies in Massachusetts’s children with similar experimental design performed between 2004-2023. Four studies (2004, 2007, 2009 and 2011) enrolled from 9 Massachusetts’s medical centers; 4 studies (2006-2007, 2010-2013, 2015-2017, and 2021-2023) enrolled at Boston Medical Center. NP swabs were collected from children between 0 and 84 months seeking well child or urgent care between October and April at their primary care site. NP samples were processed using WHO methodology.
RESULTS: Carriage prevalence and proportion of pneumococci by serotype grouping [PCV7, PCV13 unique + 6C, PCV20-additional, and nonvaccine serotypes and individual serotypes were analyzed for each study. A composite analysis of the data was created for the 20-year period. Comparing prevalence and proportion of pneumococci by serotype grouping demonstrates that while prevalence may be static or decreasing, the proportion for a specific serotype or grouping can increase. The prevalence of nonvaccine serotypes, specifically 35B, 23A and 23B, and 15A have not changed over the 20 years.
CONCLUSIONS: Prevalence of PCV7 and PCV13+ 6C serotypes declined rapidly following introduction of PCV7 and PCV13 vaccines. PCV20-additional serotype prevalence fluctuated by year but represents an increased proportion of pneumococci in the NP. Tracking individual serotypes confirms lack of cross reactivity between 23F and 23A and 23B, 9V and 9N, and 7F and 7C
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2026