The impact of pneumococcal conjugate vaccines on serotype 19A nasopharyngeal carriage

Introduction: By preventing nasopharyngeal carriage acquisition among vaccinated persons, and thus reducing transmission, pneumococcal conjugate vaccines (PCVs) provide protection against pneumococcal vaccine serotypes among unvaccinated individuals. This systematic review assessed PCVs containing serotype 19A or cross-reactive 19F for 19A carriage effects. Areas covered: Peer-reviewed literature was searched for manuscripts published between 1/1/2000 and 06/18/2018 assessing the impact of PCV on 19A carriage. Expert opinion: Fifty-five, 12, and 32 articles were identified for PCV7, PCV10, and PCV13, respectively. In two of four PCV7 randomized controlled trials (RCTs), 19A carriage was significantly higher in PCV7-vaccinated vs control subjects; in two of two PCV10 RCTs, there was no significant difference in 19A carriage and acquisition between PCV10-vaccinated (2 + 1 schedule) vs control subjects, apart from one timepoint (3 + 1 schedule); and one of one RCTs of PCV13 showed significant decreases in 19A carriage and acquisition in PCV13- vs PCV7-vaccinated (3 + 1 schedule) children. These findings were consistent with observational studies in which an increase or no change in 19A carriage was observed in 91% and 67% of PCV7 and PCV10 studies, respectively, whereas 87% of PCV13 studies documented a decrease. Countries in which serotype 19A transmission is substantial should consider the use of vaccines containing serotype 19A.