Effects of pneumococcal vaccination program on pneumococcal carriage and invasive disease

Using a cross-sectional study, Stefan Flasche and colleagues investigated the effects of the UK pneumococcal vaccination program on serotype-specific carriage and invasive pneumococcal disease. There are more than 90 Streptococcus pneumoniae serotypes that can cause invasive pneumococcal disease (IPD). The pneumococcal conjugate vaccine PCV7 contains antigens from seven serotypes responsible for IPD. Immunization with PCV7 prevents both IPD disease and carriage of these seven serotypes, but after vaccination non-vaccine serotypes could colonize the nasopharynx. There are concerns that this “serotype replacement” could reduce the benefits of vaccination. This cross-sectional study examined nasopharyngeal swabs taken from PCV7-vaccinated children and their families for S. pneumoniae, determined the serotype of any bacteria found, and compared the proportion of people carrying S. pneumoniae (carrier prevalence) and the distribution of serotypes in this study population with a similar population that was studied in 2000/1, before the PCV...