Impact of 10-valent pneumococcal conjugate vaccine on invasive pneumococcal disease and nasopharyngeal carriage in Kenya

Laura L. Hammitt, Anthony O. Etyang, Susan C. Morpeth, John Ojal, Alex Mutuku, Neema Mturi, Jennifer C. Moisi, Ifedayo M. Adetifa, Angela Karani, Donald O. Akech, Mark Otiende, Tahreni Bwanaali, Jackline Wafula, Christine Mataza, Edward Mumbo, Collins Tabu, Maria Deloria Knoll, Evasius Bauni, Kevin Marsh, Thomas N. WilliamsTatu Kamau, Shahnaaz K. Sharif, Orin S. Levine, J. Anthony G. Scott

Research output: Contribution to journalArticlepeer-review


Background 10-valent pneumococcal conjugate vaccine (PCV10), delivered at 6, 10 and 14 weeks of age, was introduced in Kenya in January 2011, accompanied by a catch-up campaign in Kilifi County for children <5 years. Coverage with ≥2 PCV10 doses in children 2-11 months was 80% in 2011 and 84% in 2016; coverage with ≥1 dose in children 12-59 months was 66% and 87%, respectively. Methods Clinical and microbiological surveillance for invasive pneumococcal disease (IPD) among admissions of all ages at Kilifi County Hospital was linked to the Kilifi Health and Demographic Surveillance System from 1999-2016. We calculated the incidence rate ratio (IRR) comparing the pre-vaccine and post-vaccine eras, adjusted for confounding, and reported percent reduction in IPD as 1-IRR. Annual cross-sectional surveys of nasopharyngeal carriage were conducted from 2009-2016. Findings Surveillance identified 667 IPD cases in 3,211,403 person-years of observation. IPD incidence in children <5 years fell sharply in 2011 following PCV10 introduction, and remained low (PCV10-type IPD: 60·8 vs 3·2/100,000 [92% reduction; 95%CI: 78, 97]; overall IPD: 81·6 vs 15·3/100,000 [68% reduction; 95%CI: 40, 83]; 1999-2010 vs 2012-2016). PCV10-type IPD also declined significantly in unvaccinated age groups (<2 months, 5-14 years, ≥15 years), with estimated reductions of 100%, 74%, and 81%, respectively. There was no significant change in the incidence of non-PCV10 type IPD. In children aged <5 years, PCV10-type carriage declined by 74% and non-PCV10-type carriage increased by 71%. Interpretation Introduction of PCV10 in Kenya resulted in a substantial reduction in PCV10-type IPD in children and adults without significant replacement disease. These findings suggest that routine infant PCV10 immunization programmes with catch-up campaigns will provide substantial direct and indirect protection in low-income settings in tropical Africa.

Original languageEnglish (US)
JournalUnknown Journal
StatePublished - Jul 18 2018


  • catch up campaign
  • invasive pneumococcal disease
  • Kenya
  • nasopharyngeal carriage
  • PHiD-CV
  • pneumococcal conjugate vaccine
  • Streptococcus pneumoniae
  • vaccine effectiveness

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)
  • Immunology and Microbiology(all)
  • Neuroscience(all)
  • Pharmacology, Toxicology and Pharmaceutics(all)

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