Abstract
The World Health Organization has selected Malawi as one of three sites to pilot the roll-out of RTS,S/AS01 in phase 4 trials. As policy discussions for the expanded use of RTS,S/AS01 continue, it will be critical to determine the performance of the vaccine according to seasonal patterns of malaria transmission in regions of Africa. Given waning vaccine efficacy over time, this secondary analysis demonstrates that administering the vaccine to children in the months prior to malaria season could maximize impact of the vaccine. We followed children (5–17 months) and infants (6–12 weeks) assigned to one of three groups: (1) vaccine with four doses; (2) vaccine with three doses; (3) control. The primary endpoint was defined as episodes of clinical malaria. During the 4-years of follow-up, 658 of 1544 (42.6%) children and infants had at least one episode of clinical malaria. With each 1-inch increase in rainfall per month there was an associated increase in the rate of malaria by 12.6% (95% CI 9.6%, 15.6%, P < 0.0001) among children and 15.9% (95% CI 12.8%, 18.9%, P < 0.0001) among infants. There was no evidence of effect modification of vaccine efficacy by precipitation (89% power).
Highlights
The WHO’s Strategic Advisory Group of Experts on Immunization (SAGE) and the Malaria Policy Advisory Committee (MPAC) for the implementation of large-scale pilot projects[1]
In April 2017, the WHO announced that Ghana, Kenya, and Malawi had been selected to participate in the Malaria Vaccine Implementation Program (MVIP) of RTS,S/AS01 beginning in 2018
Mathematical models have shown that while absolute vaccine impact would increase with increasing levels of malaria transmission, a higher proportion of averted episodes and high cost-effectiveness may be possible in lower transmission regions[10]
Summary
The WHO’s Strategic Advisory Group of Experts on Immunization (SAGE) and the Malaria Policy Advisory Committee (MPAC) for the implementation of large-scale pilot projects[1]. In April 2017, the WHO announced that Ghana, Kenya, and Malawi had been selected to participate in the Malaria Vaccine Implementation Program (MVIP) of RTS,S/AS01 beginning in 2018. Results from the MVIP will be useful before full-scale deployment across the continent To inform these policy discussions, it will be critical to understand the variation in vaccine efficacy over space and time and within different environmental contexts. Implementation of the vaccine may be effective in certain environments, such as areas where malaria transmission is high or seasonal[8]. We undertook an analysis of the phase 3 trial of RTS,S/AS01 in Lilongwe, Malawi, to evaluate its efficacy against episodes of clinical Plasmodium falciparum malaria and its effect modification by seasonal variation in precipitation
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