Background: Mortality due to severe pneumonia during childhood in resource-constrained settings is high, but data to provide basis for interventions to improve survival are limited. The objective of this study was to determine the risk factors for severe pneumonia in children aged under five years old in Mwanza, Tanzania.

Methods: We conducted a case-control study of children aged 2 to 59 months at Sekou-Toure regional hospital in Mwanza City, north-western, Tanzania from May 2013 to March 2014. Cases were children with severe pneumonia and controls were children with other illnesses. Data on demography, social-economical status, nutritional status, environmental factors, vaccination status, vitamin A supplementation and deworming, and nasopharyngeal carriage were collected and analysed using logistic regression.

Results: 117 patients were included in the study. Of these, 45 were cases and 72 controls. Cases were younger than controls, but there were no differences in social-economic or nutritional status between the two groups. In multiple regression, we found that an increased risk of severe pneumonia was associated with cooking indoors (OR 5.5, 95% CI: 1.4, 22.1), and delayed measles vaccination (OR 3.9, 95% CI: 1.1, 14.8). The lack of vitamin A supplementation in the preceding six month and Enterobacter spp nasopharyngeal carriage were not associated with higher risk of severe pneumonia. Age ≥24 months (OR 0.2, 95% CI: 0.04, 0.8) and not receiving antibiotics before referral (OR 0.3, 95% CI 0.1, 0.9) were associated with lower risk for severe pneumonia.

Conclusions: Indoor air pollution and delayed measles vaccination increase the risk for severe pneumonia among children aged below five years. Interventions to reduce indoor air pollution and to promote timely administration of measles vaccination are urgently needed to reduce the burden of severe pneumonia in children in Tanzania.