Benefit from childhood pneumococcal conjugate vaccine extends to whole population

Use of pneumococcal conjugate vaccines (PCVs) has led to substantial reductions in invasive pneumococcal disease (IPD) in high- and middle-income countries. To assess whether similar benefits are seen in a low-income country, investigators analysed the effect of 10-valent PCV on nasopharyngeal carriage and IPD in children and adults in rural Kenya. The study was done among residents covered by the Kilifi Health and Demographic Surveillance System, an existing integrated surveillance system with data from 1999 to 2016. PCV10 was introduced in January 2011, delivered to infants at ages 6, 10, and 14 weeks and via a catch-up campaign that provided at least one PCV10 dose to children aged 12 to 59 months.

Incidence of IPD in children <5 years dropped rapidly after vaccine introduction and remained low: PCV10-type IPD per 100,000 population dropped from 60.8 prevaccine (1999 through 2010) to 3.2 postvaccine (2012 through 2016), and IPD caused by any serotype dropped from 81.6 to 15.3 per 100,000. Children <5 years had an 85% reduction in bacteremic pneumococcal pneumonia and a 69% decrease in pneumococcal meningitis. IPD also declined in those aged 5 to 14 years and ≥15 years. Incidence of vaccine-type IPD also decreased in infants too young to be vaccinated. IPD incidence caused by non-PCV10 type did not increase. After vaccine introduction, childhood admissions with radiologically confirmed pneumonia decreased by 48%.

Despite multiple studies showing benefits of PCV10 in higher-income countries, this is the first to document similar findings in a low-income country. The investigators did not observe an increase in nonvaccine-type infections; this will require ongoing monitoring.