After the initial excitement about the first malaria vaccine, expectations were severely dampened when only a modest efficacy was reported. However, four years after the rollout began, it becomes clear just how many lives were saved.
Malaria continues to be one of the main causes of death in children in sub-Saharan Africa. It is estimated that almost 500,000 children under 5 died of malaria in 2021. Prevention efforts are mostly focused on reducing mosquito bites via bed nets, personal protection, or insecticides because, for a long time, there was no vaccine available. This changed with the RTS,S vaccine, the first malaria vaccine approved by the WHO. However, hopes that this vaccine would turn the tides in the fight against malaria were dampened in 2015, when a clinical trial found an efficacy of only 36,6 % in young children and infants. Moreover, the study associated the vaccine with higher rates of meningitis and rabies-related deaths.
As a result, instead of a massive rollout, the WHO initiated a pilot study in Ghana, Kenya and Malawi. Because the statistics of malaria-related deaths and illnesses are often unreliable in these countries, community reporters were sent to conduct household surveys – 14,000 of such reporters were employed in Kenya alone. They compared areas where the vaccine was being administered to areas where vaccinations were delayed.
The first results of this pilot study were already published in 2021 and they renewed a bit of optimism: The severe side-effects as a result of the RTS,S vaccine could not be replicated in this large-scale study. Still, the question of its efficacy remained.
On October 20th this year, the complete data was presented by the WHO during the annual meeting of the American Society of Tropical Medicine and Hygiene. And the results were well above all expectations – as leader of the WHO study Mary Hamel later jokingly said: “I’m surprised I didn’t hear any gasps.” Over four years, a reduction of 13 % of malaria-related deaths in young children was observed. Additionally, cases of severe malaria were reduced by 22 % in children who were old enough to have received all three shots. The director of malaria vaccine implementation at PATH (Program for Appropriate Technology in Health) commented: “What we have seen is a considerable impact of a vaccine described as having a moderate impact.”
Besides the efficacy, there were two more concerns about the vaccine. Firstly, it was feared that its addition would lead to a lower readiness to follow through with other, already existing vaccination programs, such as the one against measles. However, this effect could not be shown during the study, indicating that the malaria vaccine can readily be integrated into the routine vaccination program of children in sub-Saharan Africa.
The second concern was that the vaccination would lead to a false sense of security, thereby reducing adherence to other preventative measures such as bed nets. This, too, could be disproven with the current study. However, David Walton, US global coordinator for the President’s Malaria Initiative, also acknowledged: “We now have an additional tool and yet we are still struggling to implement the tools that we [already] have in many countries.”
Despite the surprisingly positive effect of RTS,S on child mortality, it has one big drawback: One dose comes at a cost of roughly $ 10. Thus, a three-dose regimen amounts to around $ 30 per child. Walton admitted that these prices are “formidable for many countries”. However, a new, second malaria vaccine called R-21 was recommended by the WHO just this October and is expected to be cheaper and available in greater quantities than RTS,S. This could lessen the financial burden on the affected countries.
Finally, Hamel acknowledged that RTS,S could have been administered to far more people already if distribution had not been delayed to conduct this pilot study. But she also stressed the importance of addressing the concerns regarding the vaccine’s effectiveness, impact and feasibility, because otherwise, the “questions would have lingered”. Additionally, the gathered data of this pilot study have “forged a pathway for future malaria vaccines” – such as R-21.
Image source: Jennifer Latuperisa-Andresen, Unsplash
