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 admitted to Kilifi County Hospital (KCH) and vaccination coverage in the area under study.
Graph 1 shows cases of IPD where one of the strains of bacteria targeted by the PCV10 vaccine is detected.
Graph 2 shows all cases of IPD.
Graph 3 shows coverage of PCV10 vaccine in the Kilifi Health & Demographic Surveillance System, the area under study.
Vaccine Monitoring System (VMS)
The PCVIS study (and its sub-studies) is embedded in the Vaccine Monitoring System (VMS). Starting November 2008, the VMS has continually captured all childhood vaccination information including all doses given in 34 health facilities (map below) providing childhood immunization services. We also monitor episodes of adult disease and paediatric disease with surveillance of all adults and children admitted to Kilifi County Hospital, and we monitor naso-pharyngeal carriage using swabs collected from 500 randomly selected individuals of all ages and cultured for S. pneumoniae and H. influenzae and S. aureus.
Investigators : Investigators: Anthony Scott, Laura Hammitt, Ifedayo Adetifa, Collins Tabu, Claire Gordon, Anthony Etyang, John Ojal, Gerald Ong’ayo, Micah Silaba