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

Abstract

SummaryBackgroundThe 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.MethodsPCV10 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.FindingsAbout 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).InterpretationAfter 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.FundingGAVI Alliance and Wellcome Trust.

Pneumococcal serotype distribution: A snapshot of recent data in pediatric and adult populations around the world

“…30 Conjugate vaccine serotypes causing IPD were highly prevalent (> 60% of serotypes) in 2 studies. 6,57 Prevalence of serotypes uniquely covered by PPV23 was reported in 4 studies 6,9,24,57 2 of which reported 12F to be most prevalent.…”

A Combination of Recombinant Mycobacterium bovis BCG Strains Expressing Pneumococcal Proteins Induces Cellular and Humoral Immune Responses and Protects against Pneumococcal Colonization and Sepsis

“…Tenvalent PCV (PCV10) and PCV13, specially recommended for children younger than 2 years of age, induce a high antibody response against included serotypes, protect against invasive diseases, and reduce pneumococcal carriage (4,5). One of the main limitations of these serotype-specific vaccines is the "serotype replacement" effect.…”

Valuing vaccination

“…First, vaccinations are commonly given in early life phases, and the returns on vaccination investments, such as improved school attainment, economic productivity, and social functioning, are reaped throughout the life course (31)(32)(33). Second, vaccinations often disrupt transmission chains of infectious diseases throughout the community, leading to multiplier effects for the broader economic and social benefits of vaccination (20,(39)(40)(41)(42)(43)(44)67). Third, the child survival benefits of vaccinations typically catalyze or accelerate fertility decline and create potentially sizable opportunities for economic growth.…”

“…Community health externalities include herd effects, whereby unvaccinated members of a community incur protection from disease through the vaccination of others (39)(40)(41)(42)(43)(44)(45)(46)(47). They also include reduced use of antibiotics to fight vaccine-preventable diseases and, as a consequence, slower development of antibiotic resistance (48,49).…”

“…Herd effects: Childhood PCV vaccination is likely to lead to substantial reduction in pneumococcal disease in population groups that will not routinely receive the vaccination, because it prevents the spread of the infection to these groups, e.g., the elderly and HIV-infected middle-aged adults (19,46). Evidence from studies of PCV7 and PCV10 introduction indicate reduced circulation of vaccine-specific serotypes in the population (42)(43)(44).…”