Pneumococcal nasopharyngeal carriage following reduced doses of a 7-valent pneumococcal conjugate vaccine and a 23-valent pneumococcal polysaccharide vaccine booster

Abstract

This study was conducted to evaluate the effect of a reduced-dose 7-valent pneumococcal conjugate vaccine (PCV) primary series followed by a 23-valent pneumococcal polysaccharide vaccine (23vPPS) booster on nasopharyngeal (NP) pneumococcal carriage. For this purpose, Fijian infants aged 6 weeks were randomized to receive 0, 1, 2, or 3 PCV doses. Within each group, half received 23vPPS at 12 months. NP swabs were taken at 6, 9, 12, and 17 months and were cultured for Streptococcus pneumoniae. Isolates were serotyped by multiplex PCR and a reverse line blot assay. There were no significant differences in PCV vaccine type (VT) carriage between the 3- and 2-dose groups at 12 months. NP VT carriage was significantly higher (P, <0.01) in the unvaccinated group than in the 3-dose group at the age of 9 months. There appeared to be a PCV dose effect in the cumulative proportion of infants carrying the VT, with less VT carriage occurring with more doses of PCV. Non-PCV serotype (NVT) carriage rates were similar for all PCV groups. When groups were pooled by receipt or nonreceipt of 23vPPS at 12 months, there were no differences in pneumococcal, VT, or NVT carriage rates between the 2 groups at the age of 17 months. In conclusion, there appeared to be a PCV dose effect on VT carriage, with less VT carriage occurring with more doses of PCV. By the age of 17 months, NVT carriage rates were similar for all groups. 23vPPS had no impact on carriage, despite the substantial boosts in antibody levels.

Trial registration: ClinicalTrials.gov NCT00170612.

FIG. 1.

Cumulative proportions of infants carrying a 7-valent pneumococcal conjugate vaccine (PCV) type at the ages of 6, 9, 12, and 17 months (m) by PCV and 23-valent pneumococcal polysaccharide vaccine (23vPPS) group allocation.

FIG. 2.

Nasopharyngeal (NP) carriage rates of all pneumococcal serotypes and 7-valent pneumococcal conjugate vaccine (PCV) serotypes (VT) at the age of 17 months following either no vaccination or 1, 2, or 3 doses of PCV in infancy with or without a booster consisting of a 23-valent pneumococcal polysaccharide vaccine (23vPPS) at 12 months (12m). For all comparisons within the same PCV dosage group between those receiving or not receiving 23vPPS at 12 months, P values were not significant (all >0.45).