Population effect of 10-valent pneumococcal conjugate vaccine on nasopharyngeal carriage of Streptococcus pneumoniae and non-typeable Haemophilus influenzae in Kilifi, Kenya: findings from cross-sectional carriage studies.
LANCET GLOBAL HEALTH 2014;
2:e397-405. [PMID:
25103393 PMCID:
PMC5628631 DOI:
10.1016/s2214-109x(14)70224-4]
[Citation(s) in RCA: 160] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Background
The effect of 7-valent pneumococcal conjugate vaccine
(PCV) in developed countries was enhanced by indirect protection of unvaccinated
individuals, mediated by reduced nasopharyngeal carriage of vaccine-serotype
pneumococci. The potential indirect protection of 10-valent PCV (PCV10) in a
developing country setting is unknown. We sought to estimate the effectiveness of
introduction of PCV10 in Kenya against carriage of vaccine serotypes and its effect
on other bacteria.
Methods
PCV10 was introduced into the infant vaccination programme
in Kenya in January, 2011, accompanied by a catch-up campaign in Kilifi County for
children aged younger than 5 years. We did annual cross-sectional carriage studies
among an age-stratified, random population sample in the 2 years before and 2 years
after PCV10 introduction. A nasopharyngeal rayon swab specimen was collected from
each participant and was processed in accordance with WHO recommendations. Prevalence
ratios of carriage before and after introduction of PCV10 were calculated by
log-binomial regression.
Findings
About 500 individuals were enrolled each year (total
n=2031). Among children younger than 5 years, the baseline (2009–10) carriage
prevalence was 34% for vaccine-serotype Streptococcus
pneumoniae, 41% for non-vaccine-serotype Streptococcus
pneumoniae, and 54% for non-typeable Haemophilus
influenzae. After PCV10 introduction (2011–12), these percentages were
13%, 57%, and 40%, respectively. Adjusted prevalence ratios were 0·36 (95% CI
0·26–0·51), 1·37 (1·13–1·65), and 0·62 (0·52–0·75), respectively. Among individuals
aged 5 years or older, the adjusted prevalence ratios for vaccine-serotype and
non-vaccine-serotype S pneumoniae carriage were 0·34 (95% CI
0·18–0·62) and 1·13 (0·92–1·38), respectively. There was no change in prevalence
ratio for Staphylococcus aureus (adjusted prevalence ratio for
those <5 years old 1·02, 95% CI 0·52–1·99, and for those ≥5 years old 0·90,
0·60–1·35).
Interpretation
After programmatic use of PCV10 in Kilifi, carriage of
vaccine serotypes was reduced by two-thirds both in children younger than 5 years and
in older individuals. These findings suggest that PCV10 introduction in Africa will
have substantial indirect effects on invasive pneumococcal disease.
Funding
GAVI Alliance and Wellcome Trust.
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