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

Abstract

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 postvaccine eras, adjusted for confounding, and reported percent reduction in IPD as 1-IRR. Annual crosssectional 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%.

High residual prevalence of vaccine-serotypeStreptococcus pneumoniaecarriage after introduction of a pneumococcal conjugate vaccine in Malawi: a prospective serial cross-sectional study

“…Kenya reported a reduction from 34% to 9% VT carriage among PCV-vaccinated children under 5 years of age, 6 years after introduction of 10-valent PCV. 19 The Gambia reported a reduction from 50% to 13% VT carriage among children 2-5 years old, 20 months after introducing the 7-valent PCV. 45 Likewise, a study from South Africa showed reduced PCV13serotype colonisation from 37% to 13% within 1 year of transitioning from PCV7 to PCV13.…”

“…14 Vaccine trials and post-routine-introduction studies in Africa have demonstrated substantial direct effects of PCV against IPD, pneumonia, and all-cause mortality among young children. [15][16][17][18] Although Kenya, 19 The Gambia, 18 Mozambique 20 , and South Africa 21 have reported VT carriage reductions, residual carriage prevalences are still higher than in industrialised countries. [22][23][24] In addition, there is evidence of rapid onset of NVT replacement in the region.…”

The merits of sustaining pneumococcal vaccination after transitioning from Gavi support – a modelling and cost-effectiveness study for Kenya

“…We predicted IPD incidence by multiplying modelled age-specific carriage incidence with case-to-carrier ratios (CCR). For each model posterior the CCRs were calculated as the ratio of the observed pre-vaccination IPD incidence at Kilifi Country Hospital (KCH) 3 to modelled pre-vaccination carriage incidence. The CCR were assumed to remain unchanged post-vaccination.…”

“…Pneumococcal sepsis was defined as IPD not meeting the definitions of pneumococcal meningitis or bacteraemic pneumococcal pneumonia. We further assumed that for every prevented case of IPD one would prevent 5.3 cases of clinically-defined pneumonia 3,6 . This ratio was estimated by dividing the vaccine preventable clinical pneumonia incidence (351 per 100,000 per year) 3 to vaccine preventable IPD incidence (66.3 per 100,000 per year) 6 that were both estimated from surveillance at KCH.…”

“…The majority of African countries have introduced the pneumococcal conjugate vaccines (PCVs) in their childhood immunization programmes which has led to a substantial reduction in pneumococcal disease 1,2 . In Kilifi, a coastal area in Kenya with enhanced surveillance for bacterial diseases, overall invasive pneumococcal disease (IPD) decreased by 68% in the post vaccination period (2012-2016) in children aged <5 years 3 .…”