PCVIS started in 2009 with funding from Gavi, the Vaccine Alliance, and has been conducting research for over a decade to understand the effects of PCV in Kenya.  PCVIS is a partnership between KEMRI Wellcome Trust Research Programme, Kilifi County Government Health Services Department and London School of Hygiene & Tropical Medicine.

PCVIS leverages the Kilifi Health and Demographic Surveillance System which has meticulously documented demographic information about the population of Kilifi County since 2000. This provides robust baseline and contextual data which researchers use to measure the impact of health interventions, including vaccines such as PCV. Each resident has a unique identifier allowing their demographic, hospital and laboratory data to be linked. This provides a powerful means of understanding individual and population level patterns of health and disease.

Each year over 650,000 children under age 5 die of pneumonia, an infection of the lungs – that’s more than HIV, tuberculosis and malaria combined.

Streptococcus pneumoniae, the pneumococcus bacteria, is amongst the leading causes of childhood pneumonia. It’s commonly carried in the nasopharynx (the back of the nose and throat) in healthy people, mostly children.

Pneumococcal disease occurs when the bacteria move from this harmless location to other more vulnerable parts of the body, including the lungs (pneumonia) or more invasive locations such as the blood (bacteremia and sepsis) or the membranes that surround and protect the brain (meningitis).
Vaccines targeting the outer carbohydrate capsule of Streptococcus pneumoniae have existed since the 1940s. However, these formulations of vaccine were not effective in children, who are most likely to carry the bacteria and therefore most vulnerable to infection and death by pneumococcal disease.

Since the 1990s, scientific technology has enabled the manufacture of so-called "conjugate" vaccines against pneumococcus (PCVs) that work very well in children. These PCVs link part of the outer carbohydrate capsule of the pneumococcal bacteria to a protein, which makes it possible for children to mount a strong immune response that can protect against disease.

Despite having been available for a number of years, the high cost of developing and manufacturing PCVs means that they remain some of the most expensive vaccine products on the market. For example, in the United States it costs over $720 for a child’s recommended four doses.

PCVs were licensed and used almost exclusively in high-income countries for the first decade of their existence: lower-income countries could not afford to provide them. With the help of Gavi, the Vaccine Alliance, which began subsidizing the cost of PCV for low- and middle-income countries in 2009, the vaccine has now been introduced in nearly every country in the world.

Kenya became an early adopter of PCV in 2011. PCVIS continues to be a flagship research programme providing some of the first and most rigorous evidence of how PCV works in Kenya. This is important for other low and middle-income countries because initial vaccine trials were all conducted in high-income countries and it was not known whether the vaccine would work differently in different contexts.