The impact of the 13-valent pneumococcal conjugate vaccine on pneumococcal carriage in the Community Acquired Pneumonia Immunization Trial in Adults (CAPiTA) Study

Abstract

Background

The impact of pneumococcal conjugate vaccination on the prevalence of nasopharyngeal carriage with pneumococci and other bacteria in adults is unknown. The direct effects of the 13-valent pneumococcal conjugate vaccine (PCV13) in community dwelling older adults was investigated as part of the randomized controlled Community Acquired Pneumonia immunization Trial in Adults (CAPiTA).

Methods

We determined the carriage of S. pneumoniae, S. aureus, H. influenzae, and M. catarrhalis before and at 6, 12 and 24 months post-vaccination using PCR-based methods and conventional cultures of naso- and oropharyngeal swabs in 1,006 PCV13-recipients and 1,005 controls. Serotyping of the 13 vaccine-type (VT) pneumococci was performed by PCR targeting capsular synthesis genes and quellung reaction of isolates.

Findings

Before randomization and based on PCR, 339 of 1891 subjects had nasopharyngeal carriage with any pneumococci (17.9%), and 114 of 1891 subjects (6.0%) carried a VT-pneumococci. At six months post-vaccination, VT-pneumococcal carriage was significantly lower in PCV13-recipients than in the placebo-group (RR 0.53 95%CI: 0.35-0.80; p=0.04). There was no difference between the groups at 12 and 24 months post-vaccination.Carriage of non-VT-pneumococci, S. aureus, H. influenzae, and M. catarrhalis did not change between groups.

Interpretations

In community-dwelling adults of 65 years and older, a single dose of PCV13 appears to elicit a small and temporary reduction in VT-carriage at 6 months post-vaccination. Neither replacement by non-vaccine serotypes nor impact on other nasopharyngeal bacteria was observed.