Abstract
BackgroundA recent trial with PCV-7 in a rural Gambian community showed reduced vaccine-type pneumococcal carriage in fully vaccinated compared with control communities. We measured pneumococcal polysaccharide antibody concentrations in this trial to understand further the mechanisms underlying the observed changes.MethodsA single-blind, cluster-randomized (by village) trial was conducted in 21 Gambian villages. In 11 villages, all residents received PCV-7 (Vaccine group); in 10 control villages only children <30 months old or those born during the study received PCV-7. Subjects over the age of 30 months resident in vaccine villages received a single dose of PCV-7 whilst those in control villages received a single dose of a serogroup C meningococcal conjugate vaccine. Serum antibody concentrations against specific pneumococcal polysaccharides were measured in approximately 200 age-stratified subjects before, 4–6, 12 and 24 months following vaccination.ResultsBaseline pneumococcal antibody concentrations were generally high and increased with age up to 10 years. One dose of PCV-7 increased geometric mean antibody concentrations (GMC) in vaccinated versus control villages for vaccine serotypes 6B and 18C, and 4 and 18C, in the young (under 5 years) and older age groups (5+ years) respectively. There were significantly higher proportions of subjects in the vaccinated than in the control communities with an antibody concentration believed to protect against carriage (>5.0 µg/mL) for all but serotype 9V of the PCV-7 serotypes in the older group, but not in the younger age group.ConclusionHigher antibodies in vaccinated communities provide an explanation for the lower pneumococcal carriage rates in fully vaccinated compared to control communities.Trial RegistrationControlled-Trials.com ISRCTN51695599 51695599.
Highlights
Pneumonia is one of the leading causes of mortality in children,5 years old
Population-based studies undertaken in Upper River Region, The Gambia showed an incidence rate of invasive pneumococcal disease (IPD) among infants approximately 10–20 times higher than that found in Caucasian populations in Europe and the United States of America [6,9,10]
Study Site and Recruitment of Study Participants Sera were obtained during the course of a single-blind, clusterrandomized trial conducted in 21 villages in the Sibanor district of the Western Region of The Gambia
Summary
Pneumonia is one of the leading causes of mortality in children ,5 years old. It is responsible for 1.6 million (18%) of the 8.8 million deaths annually in children in this age group [1], with 50% of these deaths occurring in sub-Saharan Africa [2]. Streptococcus pneumoniae (the pneumococcus) accounts for 30–50% of pneumonia-related deaths, and is a leading cause of death in children ,2 years of age in developing countries [3,4,5]. A recent trial with PCV-7 in a rural Gambian community showed reduced vaccine-type pneumococcal carriage in fully vaccinated compared with control communities. We measured pneumococcal polysaccharide antibody concentrations in this trial to understand further the mechanisms underlying the observed changes
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