By: Mustafa Ahmad
Edited By: Edu Kenedi
It has been a little over a year since the first significant step towards developing malaria vaccines. In July 2022, the World Health Organization (WHO) prequalified the RTS, S/AS01 (Mosquirix), as the first malaria vaccine acceptable for production and use. As many countries look towards the WHO for guidance on infectious disease strategy, this was a significant milestone in the fight against the disease. As of April 2023, at least 1 million children in Ghana, Kenya, and Malawi have received at least one dose of Mosquirix following these countries’ initial pilot programs several years earlier. Additionally, over 18 million doses have been allocated for ten additional African countries. But Mosquirix is just a first step. What is the current progress on malaria vaccines, and why is this moment an especially critical juncture to invest in malaria research?
Vaccines like Mosquirix come on the heels of decades of research and development. Early efforts focused on whole-parasite vaccines, with scientists experimenting with weakened or killed malaria parasites to stimulate an immune response. In the 1980s, the first vaccine candidate, SPf66, showed promise but was not as effective as hoped. Subsequent research shifted toward subunit vaccines that targeted specific components of the Plasmodium parasite, such as the circumsporozoite protein. In 2015, Mosquirix, developed by GlaxoSmithKline, became the first malaria vaccine to receive a positive opinion from the European Medicines Agency (EMA) before its eventual approval by the WHO.
Despite the promise of Mosquirix, scientists believe that the development of vaccines must continue. For starters, most malaria vaccine efforts have focused on P. falciparum, the more common mosquito-borne parasite responsible for most malaria cases. However, other mosquito-borne parasites, such as P. vivax, also merit attention for clinical trials for malaria vaccines. While Mosquirix offers a critical first step, there are still some ways to go before there are enough malaria vaccines that cover the full spectrum of parasites. Moreover, as most vaccines in development are live attenuated vaccines, that is, they contain a more dormant strain of the parasite, there is a risk of vaccine-resistant malaria strains emerging. This issue, combined with the growing burden of malaria, should be an impetus for further research.
To date, malaria prevention has primarily consisted of mosquito vector control. Initially, vector control was primarily done through spraying DDT, a now-banned chemical linked to increased risk of different types of cancers, on crops. Modern vector control includes insecticide-treated nets (ITN) and indoor residual spraying (IRS). Vector control methods like ITN and IRS remain a critical part of malaria reduction and elimination campaigns, even though their effectiveness is often questioned. However effective it may or may not be, vector control must be coupled with effective malaria vaccines in controlling long-term malaria infection rates.
In the 21st century, malaria primarily remains a leading cause of death in lower-income countries. As evidenced by how rapidly several countries have moved to provide or allocate resources for Mosquirix, many affected nations are eager to figure out how to integrate malaria vaccines into their health systems. However, even in areas that have seen their fair share of mosquito-borne diseases, malaria is predicted to surge as climates get warmer. This has been observed at local, national, and global levels. In Africa, for example, the burden is predicted to shift from west Africa to eastern and southern Africa. In Asia, the malaria burden is expected to drastically increase across eastern India, Bangladesh, and most of Southeast Asia.
Additionally, this does not mean the disease has diminished as a looming feature in emerging countries or as a threat in higher-income countries. Climate change threatens to amplify mosquito-borne diseases overall, and malaria is predicted to have some of the most devastating impacts on populations in the future. In particular, the southern United States, south and south-Eastern Europe, and Australia are being eyed as potential hotspots. It is crucial, then, that in the past year and a half, malaria vaccines have made progress. Tracking this progress and the present opportunities and challenges will be critical as malaria threatens to resurge after decades or even centuries in many parts of the world. Wealthier nations, in particular, would take care to heed this warning and be proactive rather than feel assured that they are protected.