Changing incidence of invasive pneumococcal disease in infants less than 90 days of age before and after introduction of the 13-valent Pneumococcal Conjugate Vaccine in Blantyre, Malawi: a 14-year hospital based surveillance study

BackgroundInvasive pneumococcal disease (IPD) in young infants is uncommon but associated with high morbidity and mortality. Accurate data on the burden of IPD in young infants in low-income countries are lacking. We examined the burden of IPD in infants aged <90 days in Blantyre, Malawi over a 14 year period and evaluated the impact of the 12 November 2011 introduction of the 13-valent pneumococcal conjugate vaccine (PCV13) on vaccine-serotype IPD (VT-IPD) in this population. MethodsWe conducted laboratory-based prospective IPD surveillance in infants aged <90 days admitted to Queen Elizabeth Central Hospital (QECH) in Blantyre between 2005 and 2018, including 7 years pre- and 7 years post-PCV13 introduction. IPD was defined as Streptococcus pneumoniae identified by culture from blood or cerebrospinal fluid. Serotypes were determined by multiplex PCR and latex agglutination testing. ResultsWe identified 130 cases of culture-confirmed IPD in infants <90 days old between 2005-2018. Total IPD incidence was declining prior to PCV13 introduction. The mean incidence of IPD was significantly lower in the post-PCV era. Serotypes 5 (27.8%) and 1(15.6%), were most prevalent. Even after PCV13 introduction, VT-IPD remained dominant with serotype 5 accounting for 17.4% and serotype 1 for 13% of cases in young infants. ConclusionVaccine serotypes were the main cause of IPD in neonates and young infants, both before and after PCV13 introduction. Further strategies need to be considered to protect this vulnerable population, including maternal or neonatal immunization and implementation of an alternative PCV schedule with a booster dose. SummaryThe incidence of invasive pneumococcal disease in infants in Blantyre, Malawi has declined over the past decade and more significantly after introduction of the pneumococcal conjugate vaccine. Vaccine serotypes have remained the main cause of disease in this population.