Pneumococcal Conjugate Vaccine Impact Study (PCVIS)
The Pneumococcal Conjugate Vaccine Impact Study (PCVIS) is a large-scale before-after study of the impact of 10-valent pneumococcal conjugate vaccine (PCV10) in Kenya. It is one of the first population-level studies looking at the impact of PCV10 on childhood pneumonia and pneumococcal disease protection in a lower-middle income country.
PCV10 was introduced into the routine infant vaccination programme in Kenya in January 2011, accompanied by a catch-up campaign in Kilifi County for children under five.
PCVIS gathers vaccine coverage data, and compares the incidence rates of invasive pneumococcal disease, clinically-defined and radiologically proven pneumonia, and all-cause admissions to Kilifi County Hospital before and after vaccine introduction.
The study measures the direct impact of PCV10 among vaccinated individuals and any indirect protection on the unvaccinated population afforded by the vaccine. Early on, PCVIS established the safety of PCV10 in a field setting, and more recently, PCVIS has been tracking serotype replacement disease.
PCVIS also models the cost effectiveness of PCV10, and future research will investigate how the vaccine could be administered effectively at a lower unit cost. This is an important consideration because PCV10 is the most expensive vaccine in the childhood immunization programme in Kenya, and subsidy will start to be reduced from 2021.
The graphs below show the cases of invasive pneumococcal disease (IPD) in children and adults admitted to Kilifi County Hospital (KCH).
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Between November 2008 and December 2017, the Kilifi Vaccine Monitoring Study (KiVMS) continually captured all childhood vaccination information including all doses given in 34 health facilities providing childhood immunization services. KiVMS was replaced by the Kilifi Electronic Immunization Registry (KEIR). KEIR is operational in 27 health facilities within the Kilifi Health and Demographic Surveillance System (KHDSS) and is implemented by Kilifi County Department of Health staff with support from a team of PCVIS staff.
We monitor episodes of adult and paediatric disease with surveillance of all adults and children admitted to Kilifi County Hospital. We also monitor nasopharyngeal carriage of S. pneumoniae and other bacteria in addition to collecting serological samples for assessment of population immunity to pneumococcus.