Preliminary Analysis of the Impact of Malaria Vaccine Introduction on Severe Malaria Incidence in Children Under 5 Years in the Health Districts of Edea, Japoma, and Mbanga (2020–2024)
Alex Stéphane Ndjip Ndjock, Michaela Josee Meli, Nina Ngouenko Nkakoua, Steve Roland Souga, Prince Théophile Djomou, Marie‐Michelle Ekedy‐Lea, Esther Laura Nyame Dipepa NwallABSTRACT
Background and Aims
The RTS,S/AS01 malaria vaccine (MV) was introduced in Cameroon on 22 January 2024 in 42 of 200 health districts, including three in the Littoral Region (Edea, Japoma and Mbanga). This study describes early trends in severe malaria among children under 5 years of age in these three districts of the Littoral Region and explores their relation to district‐level MV coverage.
Methods
Retrospective ecological time‐trend study of routine DHIS 2 data, 2020–2024. Annual confirmed severe and uncomplicated malaria cases were described by district; 2024 was compared with 2023 and with the 2020–2023 mean. MV1–MV3 coverage and dropout were computed for 2024. MV3 coverage and the percentage change in severe cases (n = 3 districts) were explored with Pearson's correlation (exact p‐value and 95% confidence interval) and Spearman's rank correlation.
Results
Severe cases rose by 11.2% in 2024 (6,106 to 6,792) after declines of 4.7% in 2022% and 7.0% in 2023; the 2024 total was 10.3% above the 2020–2023 mean, and the rise was smaller than that between 2020 and 2021 (+ 35.8%). Increases were 14.4% in Edea, 11.5% in Japoma and 4.2% in Mbanga. MV3 coverage was 37.5%, 28.8% and 32.0%, respectively; 44.6% of children who received MV1 had not received MV3 (range 33.8%–59.3%). MV3 coverage was not informatively associated with the change in severe cases (Pearson r = 0.41, 95% CI − 0.92 to 0.97, p = 0.73; Spearman ρ = 0.50, exact p = 1.00); with three districts the analysis has virtually no power.
Conclusion
No change in severe malaria attributable to the vaccine was detectable in its first year, as expected given recent introduction and low, incomplete coverage. The 2024 increase lies within earlier year‐to‐year variation and cannot be attributed to, or against, the vaccine. Dropout between the first and third doses is substantial. Impact evaluation requires monthly time‐series analyses with comparison districts, population denominators and longer follow‐up.