Abstract
This systematic review and meta-analysis aims to quantify the impact of vaccination on the incidence and prevalence of nonsusceptible infections and investigates the impact of vaccination programs on serotype replacement. We searched a comprehensive set of databases. Identified studies were assessed using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) approach and resulting evidence was analyzed using random-effect meta-analyses. Nineteen studies on pneumococcal conjugate vaccines (PCV) met our inclusion criteria. PCV decreases the incidence of nonsusceptible pneumococcal infections (PIs) by 56.91% (95% confidence interval [CI], -50.90% to -62.91%) and the probability of carriage of nonsusceptible pneumococcal bacteria by 28.10% (95% CI, -13.25% to -42.95%). The effect of PCV on PIs becomes higher when only serotypes specifically targeted by the vaccine are taken into account (-80.98%; 95% CI, -70.34% to -91.52%), while it becomes lower when all the PIs, including both susceptible and nonsusceptible PIs, are considered (-48.30%; 95% CI, -31.55% to -65.08%). The effect of PCV is found greater in populations with high prevalence of human immunodeficiency virus and for PCV covering a higher number of serotypes. Findings from this study suggest that vaccination programs may be an effective tool to prevent the spread of PIs and may play a significant role in tackling antimicrobial resistance.