Household Air Pollution (HAP) is Associated With Increased Pneumococcal Carriage in Malawian Infants – Malawi Streptococcus pneumoniae Carriage and Air Pollution Exposure (MSCAPE) Study

Background: Household air pollution (HAP) from solid cooking fuels is a risk factor for childhood pneumonia. Nasopharyngeal carriage of Streptococcus pneumoniae is a necessary step in development of pneumococcal pneumonia. We hypothesised that HAP influences S. pneumoniae carriage. MSCAPE assesses the relationship between HAP from solid cooking fuels and prevalence/density of S. pneumoniae carriage among children. Methods: MSCAPE is a prospective study of children participating in a trial of a cleaner burning cookstove to reduce childhood pneumonia incidence in Malawi (CAPS). MSCAPE assessed the impact of HAP exposure on prevalence of S. pneumoniae carriage in 6 week and 6 month old children through intention-to-treat and adjusted exposure-response analyses. Exposure to HAP (PM2·5) was assessed through RTI Micropem and S. pneumoniae detection in nasopharyngeal swabs. Findings: S. pneumoniae carriage prevalence was 39% (n=89) and 85% (n=398) in 6 week and 6 month old children respectively. A higher mean PM2·5 exposure was observed in intervention children (53·9 µg/m3) than controls (49·0 µg/m3), although not significant (p>0.05). Intention-to-treat analysis found a non-significant increased risk of S. pneumoniae carriage in intervention children (OR=1·36; 95% CI:0·97, 1·92). Exposure-response analysis found a significant association between HAP exposure and S. pneumoniae carriage with a 10% increase in risk per decile of PM2·5 exposure (OR=1·10; 95% CI:1·01, 1·20, p=0·035). Interpretation: Despite the lack of observed impact from the cleaner burning cookstove intervention, HAP exposure (PM 2·5) was significantly associated with S. pneumoniae prevalence giving empirical evidence for the potential mechanistic relationship between HAP and childhood pneumonia. Funding Statement: This work was supported by Bill and Melinda Gates Foundation through grant number OPP1131425. The CAPS was funded by a Joint Global Health Trials Grant from the Medical Research Council, the UK Department for International Development and Wellcome Trust (MR/K006533/1). Declaration of Interests: There are no financial competing interests in relation to the work described. Ethics Approval Statement: Ethical approval was provided by the College of Medicine Research and Ethics Committee (COMREC), Malawi (P.08/15/1794) and the Central Ethics Committee of the University of Liverpool (RETH000839).