Abstract
SummaryBackgroundLittle information is available about the effect of pneumococcal conjugate vaccines (PCVs) in low-income countries. We measured the effect of these vaccines on invasive pneumococcal disease in The Gambia where the 7-valent vaccine (PCV7) was introduced in August, 2009, followed by the 13-valent vaccine (PCV13) in May, 2011.MethodsWe conducted population-based surveillance for invasive pneumococcal disease in individuals aged 2 months and older who were residents of the Basse Health and Demographic Surveillance System (BHDSS) in the Upper River Region, The Gambia, using standardised criteria to identify and investigate patients. Surveillance was done between May, 2008, and December, 2014. We compared the incidence of invasive pneumococcal disease between baseline (May 12, 2008–May 11, 2010) and after the introduction of PCV13 (Jan 1, 2013–Dec 31, 2014), adjusting for changes in case ascertainment over time.FindingsWe investigated 14 650 patients, in whom we identified 320 cases of invasive pneumococcal disease. Compared with baseline, after the introduction of the PCV programme, the incidence of invasive pneumococcal disease decreased by 55% (95% CI 30–71) in the 2–23 months age group, from 253 to 113 per 100 000 population. This decrease was due to an 82% (95% CI 64–91) reduction in serotypes covered by the PCV13 vaccine. In the 2–4 years age group, the incidence of invasive pneumococcal disease decreased by 56% (95% CI 25–75), from 113 to 49 cases per 100 000, with a 68% (95% CI 39–83) reduction in PCV13 serotypes. The incidence of non-PCV13 serotypes in children aged 2–59 months increased by 47% (−21 to 275) from 28 to 41 per 100 000, with a broad range of serotypes. The incidence of non-pneumococcal bacteraemia varied little over time.InterpretationThe Gambian PCV programme reduced the incidence of invasive pneumococcal disease in children aged 2–59 months by around 55%. Further surveillance is needed to ascertain the maximum effect of the vaccine in the 2–4 years and older age groups, and to monitor serotype replacement. Low-income and middle-income countries that introduce PCV13 can expect substantial reductions in invasive pneumococcal disease.FundingGAVI's Pneumococcal vaccines Accelerated Development and Introduction Plan (PneumoADIP), Bill & Melinda Gates Foundation, and the UK Medical Research Council.
Highlights
In South Africa, where the population has a high prevalence of HIV infection, the introduction of the 7-valent pneumococcal conjugate vaccines (PCVs) (PCV7) was associated with reduced rates of invasive pneumococcal disease in young children and adults
A Gambian trial9 of a 9-valent PCV (PCV9), which ended in 2004, showed 77% efficacy against invasive pneumococcal disease caused by vaccine serotypes, 50% against invasive pneumococcal disease overall, 37% against radiological pneumonia, and 16% against overall mortality
Our analysis showed that coverage of two or more doses of pneumococcal conjugate vaccine before 12 months of age in children born in the last 6 months of 2013 was 94% (3151/3364)
Summary
In 2008, an estimated 541 000 children younger than 5 years died from pneumococcal disease worldwide. Africa accounted for 57% of these deaths. Pneumococcal conjugate vaccines (PCVs) have been effective in highincome countries, reducing the incidence of invasive pneumococcal disease in both vaccinated and unvaccinated individuals. low-income countries have introduced PCV5 into their routine immunisation programmes and robust assessment of their effect is a priority.In South Africa, where the population has a high prevalence of HIV infection, the introduction of the 7-valent PCV (PCV7) was associated with reduced rates of invasive pneumococcal disease in young children and adults. The Gambia has a high burden of pneumococcal disease and low HIV prevalence. A Gambian trial of a 9-valent PCV (PCV9), which ended in 2004, showed 77% efficacy against invasive pneumococcal disease caused by vaccine serotypes, 50% against invasive pneumococcal disease overall, 37% against radiological pneumonia, and 16% against overall mortality. In South Africa, where the population has a high prevalence of HIV infection, the introduction of the 7-valent PCV (PCV7) was associated with reduced rates of invasive pneumococcal disease in young children and adults.. A Gambian trial of a 9-valent PCV (PCV9), which ended in 2004, showed 77% efficacy against invasive pneumococcal disease caused by vaccine serotypes, 50% against invasive pneumococcal disease overall, 37% against radiological pneumonia, and 16% against overall mortality Based on these results, and WHO recommendations, the Government of The Gambia introduced PCV7 into the national expanded programme of immunisation (EPI) on Aug 19, 2009, with a schedule of three doses at ages 2, 3, and 4 months, coadministered with the DTPw–HepB–Hib vaccine.
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