Using pneumococcal carriage and invasiveness to inform vaccine policy in tropical Africa

Children in tropical Africa carry multiple strains of pneumonia-causing bacteria in their noses, and researchers want to use those harmless carriage samples to predict which strains will cause deadly disease. Pneumococcal conjugate vaccines work well in clinical trials, but their real-world impact varies wildly across African countries. Most nations lack the expensive surveillance systems needed to track invasive disease—where bacteria escape the nose and infect blood or brain. This project turns a weakness into a strength: instead of waiting for sick children to reach hospitals, researchers will swab healthy children’s noses and use the bacteria they find there to estimate disease burden. By analysing existing data on carriage and invasive disease, the team will calculate each serotype’s “invasiveness”—how likely it is to cause severe illness when carried. They will then run carriage surveys in the Democratic Republic of Congo, Ethiopia, and Nigeria, convert those results into disease estimates, and feed them into transmission models that predict which vaccination policies would work best locally. If successful, this approach could replace costly invasive-disease surveillance with cheap, repeatable carriage studies. That would let African health ministries optimise vaccine programmes without waiting for children to die. The researchers will also test key assumptions—whether a single dominant strain drives invasion, and whether serotype alone determines risk—using stored samples from Kilifi, Kenya.