Improving capture of vaccine history: Case study from an evaluation of 10-valent pneumococcal conjugate vaccine introduction in Kenya

With the accelerated introduction of new vaccines in low-income settings, understanding immunization program performance is critical. We sought to improve immunization history acquisition from Ministry of Health vaccination cards during a vaccine impact study of 10-valent pneumococcal conjugate vaccine on pneumococcal carriage among young children in Kenya in 2012 and 2013. We captured immunization history in a low proportion of study participants in 2012 using vaccination cards. To overcome this challenge, we implemented a household-based reminder system in 2013 using community health workers (CHWs), and increased the retrieval of vaccine cards from 62% in 2012 to 89% in 2013 (P < 0.001). The home-based reminder system using CHWs is an example of an approach that improved immunization history data quality in a resource-poor setting.