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Malaria vaccines are being introduced into routine child immunisation schedules in Africa in 2024. Other prevention measures such as mosquito bednets and insecticides must continue to be used in conjunction with the vaccines, to maximise impact on the disease.
The burden of malaria is heaviest in Africa. In 2022, 94% of 249 million global malaria cases and 95% of 608 000 malaria-related deaths occurred in Africa, and more than three-quarters of deaths occurred in children younger than 5 years. In the face of such a major health challenge, WHO, through their Accelerated Malaria Vaccines Introduction and Rollout in Africa initiative, plan to introduce the Plasmodium falciparum RTS,S/AS01 (RTS,S) and R21/Matrix-M (R21) vaccines into routine immunisation schedules for children from age 5 months in 19 African countries.
The first country to introduce the routine vaccination programme was Cameroon, on Jan 22, 2024. As of Feb 9, 2024, nearly 10 000 children in Cameroon and Burkina Faso have received the RTS, S vaccine. RTS,S and R21 have not been compared in head-to-head trials, therefore the choice of vaccine will be based on supply and affordability, according to WHO.
The implementation of malaria vaccines in Africa represents an important step in the fight against the disease. James G Beeson (Burnet Institute, Melbourne, VIC, Australia) commented “The vaccines [are] important for reducing malaria in young children, providing an important new tool to combat malaria. [They are] also important in establishing a foundation we can build on as we work towards next-generation vaccines that could accelerate malaria elimination.” Anders Björkman (Karolinska Institutet, Stockholm, Sweden) added “The vaccine(s) will provide a significant reduction of clinical episodes and probably also incidence of severe malaria for up to 3 years after primary vaccination. This will have a significant impact on the wellbeing of the children [and] also some relief for the parents and health-care centres.”
The efficacy and safety of both vaccines have been assessed in large-scale clinical trials; additionally RTS,S has been deployed and monitored in the pilot Malaria Vaccine Implementation Programme (MVIP) in Ghana, Kenya, and Malawi since 2019. In a media briefing, WHO and Gavi, the Vaccine Alliance, noted the efficacy of the vaccines in clinical trials as around 75% against malaria episodes 12 months after administration when given seasonally with seasonal malaria chemoprevention in areas of high transmission, and stated that the MVIP had decreased all-cause mortality in eligible children by 13%. However, they also warned that the vaccines are not a “silver bullet” against the disease, emphasising “the vaccines have to be used in combination with other malaria prevention and response measures such as bednets and indoor spraying of insecticides.”
One of the reasons for caution is that efficacy of the vaccines decreases substantially over 12–18 months. Beeson noted “Booster doses of the vaccine are important in young children.” The routine immunisation schedule consists of four doses, with a fifth dose given 1 year after dose 4 in areas where there is a substantial remaining risk for malaria in children. Some of the challenges posed include ensuring that the right information reaches communities and parents, and the related costs. Olugbenga A Mokuolu (University of Ilorin Teaching Hospital, Ilorin, Nigeria) said “Funding for vaccine administration and related messaging is going to require continuous advocacy.” Safety monitoring of the routine programme will also need to be rigorous, as some data from clinical trials of RTS,S suggested higher all-cause mortality in vaccinated girls compared with control girls, although Beeson noted that WHO’s assessment of the larger MVIP database indicated that mortality was not higher in vaccinated girls. Mokuolu said “The overall history of vaccine deployment is short, hence we have to continue learning and ensure [the] safety of everyone who receives the vaccine.”
Additionally, Björkman expressed surprise at the 13% reduction in mortality reported by WHO with RTS,S in the MVIP programme after 3 years, commenting that the programme achieved “a 7% reduction of child mortality within an average of 1 year follow-up after vaccination.” He continued “These important data and analyses are, however, not provided open access and will only be released after scientific publication, which may take several years. This is not acceptable since they are expected to impact major public health policies.” Clearly, ongoing analyses of data from the routine programmes will be essential regarding efficacy and safety monitoring of the vaccines.
It is hoped the routine vaccine rollout in Africa will not only reduce the burden of malaria in children, but also provide an evidence base to develop more effective and longer-lasting vaccines in the future. Mokuolu commented “Malaria vaccines hold the potential for accelerating efforts towards malaria elimination. [They] are an important complementary intervention to existing tools. Deployment must be focused, robust, and sustained while we continue to learn on improving the tools of malaria warfare.”