PA-711 Assessment of effectiveness of the RTS,S/AS01 malaria vaccine using the case-control approach: lessons learned from malaria vaccine pilot evaluation (MVPE) in Ghana, Kenya, and Malawi

• Published in: BMJ global health Vol. 8; no. Suppl 10; pp. A113 - A114
• Main Authors: Gyan, Thomas, Akech, Samuel, Mathanga, Don P, Kwambai, Titus, Stanley, Christopher, Adeniji, Elisha, Fogelson, Ari, Khazenzi, Cynthia, Kawaye, Jeromy, Harrison, Samuel, Musa, Monica, Hamza, Anwar Sadat, Snell, Paul, Mvalo, Tisungane, Msuku, Harrison, Collymore, Yvette, Nkumama, Irene, Kariuki, Simon, Milligan, Paul, Asante, Kwaku Poku
• Format: Journal Article
• Language: English
• Published: London BMJ Publishing Group Ltd 17-12-2023; BMJ Publishing Group LTD
• Subjects: Abstracts of Poster and e-Poster Presentations; Immunization; Malaria; Vaccines; Kenya; Malawi; Ghana
• ISSN: 2059-7908
• DOI: 10.1136/bmjgh-2023-EDC.277

BackgroundThe RTS,S/AS01 malaria vaccine was introduced in Ghana, Kenya, and Malawi in 2019. Evaluation includes case-control studies designed to monitor individual-level safety and effectiveness to complement population-level estimates derived from the MVPE. Here, we discuss design and practical considerations for conducting case-control studies to measure vaccine effectiveness against severe malaria, the need for a 4th dose, and for assessment of safety outcomes. MethodsFor the severe malaria study we aimed to estimate the effectiveness of the primary 3 doses, and of the 4th dose. We also aimed to estimate rebound, if any, in children who received only the primary 3 doses. Cases were patients with severe malaria admitted to a study hospital, residing in an RTS,S/AS01 implementation area, and eligible to have received the 3rd or 4th dose of the vaccine. The case patient’s home is visited to collect data on vaccination status and other details. Four controls are then recruited from the same community, matched closely on date of birth. Vaccination status is determined from home-based records, and from clinic registers. Similar approaches were used for studies of safety outcomes. ResultsWe share preliminary results and discuss the challenges encountered and lessons learned about implementing a multi-centre case control study for a malaria vaccine, and approaches to data collection which have proved effective, including establishing surveillance, the use of specific case definitions standardized across centres, recruiting closely age-matched community controls, and obtaining reliable information from both cases and controls on potential confounding factors which may be associated with both risk of the outcome and with access to vaccination. ConclusionCase control studies are an efficient means of monitoring vaccine effectiveness and safety, but require care in design and implementation. The lessons learned from the malaria vaccine pilots will be useful for countries planning introduction of a malaria vaccine.