Direct effect of 10-valent conjugate pneumococcal vaccination on pneumococcal carriage in children Brazil

10-valent conjugate pneumococcal vaccine/PCV10 was introduced in the Brazilian National Immunization Program along the year of 2010. We assessed the direct effectiveness of PCV10 vaccination in preventing nasopharyngeal/NP pneumococcal carriage in infants.

A cross-sectional population-based household survey was conducted in Goiania Brazil, from December/2010-February/2011 targeting children aged 7-11 m and 15-18 m. Participants were selected using a systematic sampling. NP swabs, demographic data, and vaccination status were collected from 1,287 children during home visits. Main outcome and exposure of interest were PCV10 vaccine-type carriage and dosing schedules (3p+0, 2p+0, and one catch-up dose), respectively. Pneumococcal carriage was defined by a positive culture and serotyping was performed by Quellung reaction. Rate ratio/RR was calculated as the ratio between the prevalence of vaccine-types carriage in children exposed to different schedules and unvaccinated for PCV10. Adjusted RR was estimated using Poisson regression. PCV10 effectiveness/VE on vaccine-type carriage was calculated as 1-RR*100.

The prevalence of pneumococcal carriage was 41.0% (95%CI: 38.4-43.7). Serotypes covered by PCV10 and PCV13 were 35.2% and 53.0%, respectively. Vaccine serotypes 6B (11.6%), 23F (7.8%), 14 (6.8%), and 19F (6.6%) were the most frequently observed. After adjusted for confounders, children who had received 2p+0 or 3p+0 dosing schedule presented a significant reduction in pneumococcal vaccine-type carriage, with PCV10 VE equal to 35.9% (95%CI: 4.2-57.1; p = 0.030) and 44.0% (95%CI: 14.-63.5; p = 0.008), respectively, when compared with unvaccinated children. For children who received one catch-up dose, no significant VE was detected (p = 0.905).

PCV10 was associated with high protection against vaccine-type carriage with 2p+0 and 3p+0 doses for children vaccinated before the second semester of life. The continuous evaluation of carriage serotypes distribution is likely to be useful for evaluating the long-term effectiveness and impact of pneumococcal vaccination on serotypes reduction.