Persistent Circulation of Vaccine Serotypes and Serotype Replacement After 5 Years of Infant Immunization With 13-Valent Pneumococcal Conjugate Vaccine in the United Kingdom

Abstract

Background: Following programmatic introduction of the 13-valent pneumococcal conjugate vaccine (PCV13), there is residual carriage and disease due to PCV13-covered serotypes.

Methods: PCV13-immunized children aged 13-48 months, N = 988, were enrolled between February 2014 and August 2015 ("late PCV13"), and had nasopharyngeal pneumococcal carriage compared with 7-valent pneumococcal conjugate vaccine (PCV7) immunized children, N = 567, enrolled between November 2010 and September 2011 ("early PCV13"). Nasopharyngeal pneumococci were molecular-serotyped by microarray. Invasive pneumococcal disease (IPD) cases were identified through enhanced national surveillance.

Results: Compared with PCV7-immunized children, carriage among PCV13-immunized children was significantly lower for serotypes 19A (odds ratio [OR], 0.08 [95% confidence interval {CI}, .02-.25]), 6C (OR, 0.11 [95% CI, .03-.32]), and 7F (8 vs 0 cases). IPD incidence in children <5 years was significantly lower for serotypes 1 (incidence rate ratio [IRR], 0.03 [95% CI, 0-.19]) and 7F (IRR, 0.13 [95% CI, .05-.36]) but not 19A (IRR, 0.6 [95% CI, .3-1.12]) or serotype 3 (IRR, 2.3 [95% CI, .86-6.15]) in the late PCV13 period than in the early PCV13 period. The most significant rises in IPD incidence were for serotypes 8, 12F, and 24F.

Conclusions: PCV13 has reduced serotype 19A carriage among vaccinated children. We found no impact of PCV13 on serotype 3 carriage or disease, and emergence of non-PCV13-serotype disease.

Keywords: adults; carriage; children; disease; invasive; pneumococcus; seroprevalence.