Impact of 10-valent pneumococcal conjugate vaccine introduction on pneumococcal carriage and antibiotic susceptibility patterns among children aged <5 years and adults with human immunodeficiency virus infection: Kenya, 2009-2013

Background. Kenya introduced 10-valent pneumococcal conjugate vaccine (PCV10) among children <1 year in 2011 with catch-up vaccination among children 1-4 years in some areas. We assessed changes in pneumococcal carriage and antibiotic susceptibility patterns in children <5 years and adults. Methods. During 2009-2013, we performed annual cross-sectional pneumococcal carriage surveys in 2 sites: Kibera (children <5 years) and Lwak (children <5 years, adults). Only Lwak had catch-up vaccination. Nasopharyngeal and oropharyngeal (adults only) swabs underwent culture for pneumococci; isolates were serotyped. Antibiotic susceptibility testing was performed on isolates from 2009 and 2013; penicillin nonsusceptible pneumococci (PNSP) was defined as penicillin-intermediate or -resistant. Changes in pneumococcal carriage by age (<1 year, 1-4 years, adults), site, and human immunodeficiency virus (HIV) status (adults only) were calculated using modified Poisson regression, with 2009-2010 as baseline. Results. We enrolled 2962 children (2073 in Kibera, 889 in Lwak) and 2590 adults (2028 HIV+, 562 HIV−). In 2013, PCV10-type carriage was 10.3% (Lwak) to 14.6% (Kibera) in children <1 year and 13.8% (Lwak) to 18.7% (Kibera) in children 1-4 years. This represents reductions of 60% and 63% among children <1 year and 52% and 60% among children 1-4 years in Kibera and Lwak, respectively. In adults, PCV10-type carriage decreased from 12.9% to 2.8% (HIV+) and from 11.8% to 0.7% (HIV−). Approximately 80% of isolates were PNSP, both in 2009 and 2013. Conclusions. PCV10-type carriage declined in children <5 years and adults post-PCV10 introduction. However, PCV10-type and PNSP carriage persisted in children regardless of catch-up vaccination.