The impact of 10-valent Pneumococcal Conjugate Vaccine on the incidence of radiologically-confirmed pneumonia and clinically-defined pneumonia in Kenyan children.
BackgroundPneumococcal conjugate vaccines (PCV) are highly protective against invasive pneumococcal disease caused by vaccine serotypes but the burden of pneumococcal disease in developing countries is dominated by pneumonia, most of which is non-bacteraemic. We examined the impact of PCV on pneumonia incidence.\n\nMethodsWe linked prospective hospital surveillance for clinically-defined WHO severe or very-severe pneumonia at Kilifi County Hospital from 2002-2015 to population surveillance at Kilifi Health and Demographic Surveillance System, comprising 45,000 children aged <5 years. Chest radiographs were read according to a WHO standard. A 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PCV10) was introduced in Kenya in January 2011. In Kilifi, there was a catch-up campaign for children aged <5 years. We estimated the impact of PCV10 on pneumonia incidence through interrupted time series analysis accounting for seasonal and temporal trends.\n\nFindingsThe incidence of admission with clinically-defined pneumonia in 2002/3 was 21{middle dot}7/1000/year in children aged 2-59 months. This declined progressively over 13 years. By the end of March 2011, 61{middle dot}1% of children aged 2-11 months received [≥]2 doses and 62{middle dot}3% of children aged 12-59 months received [≥]1 dose of PCV10. Adjusted incidence rate ratios for admissions with radiologically-confirmed pneumonia, clinically-defined pneumonia, and diarrhoea (control condition), associated with PCV10 introduction, were 0{middle dot}52 (95% CI 0{middle dot}32-0{middle dot}86), 0{middle dot}73 (95% CI 0{middle dot}54-0{middle dot}97) and 0{middle dot}63, (95% CI 0{middle dot}31-1{middle dot}26), respectively. The annual incidence of clinically-defined pneumonia in December 2010 was 12{middle dot}2/1000; this was reduced by 3{middle dot}3/1000 with PCV10 introduction.\n\nInterpretationOver 13 years, hospitalisations for clinically-defined pneumonia declined progressively at Kilifi County Hospital but fell abruptly by 27% in association with PCV10 introduction. The incidence of radiologically-confirmed pneumonia fell by 48%. The burden of childhood pneumonia in Kilifi, Kenya, has been reduced substantially by PCV10.\n\nFundingGavi, Wellcome Trust