Written by Kerre A. Willsher, PhD
The 39 countries that have eliminated Malaria cannot afford to become complacent (World Health Organization, 2021), and nor can anyone else. With continuous exposure to Malaria, people develop some immunity to it. However, when Malaria is eliminated, the population does not have exposure and begin to lose their immunity (World Health Organization, 2021). If there is a recurrence of Indigenous Malaria, the risk of severe or fatal illness greatly increases. This problem has occurred in countries that had eliminated or partly eliminated Malaria. Timor Leste which reported zero Indigenous cases of Malaria in 2018-2019 had problems in 2020 when there was an outbreak along its border with Indonesia (World Health Organization, 2021).
The Malaria parasite mutates and continues to develop resistance to anti-malarial medications. At the same time, Anopheles mosquitoes become resistant to vector control sprays. The progress on Malaria elimination/eradication is tenuous at the best of times and is now more difficult with the advent of Covid 19. The aforementioned scenarios stress the need for multiple strategies in fighting Malaria, including effective vaccines (World Health Organization, 2021).
So why has it taken so long?
The life cycle of the Malaria plasmodium is complex with an enormous reserve of polymorphic proteins (Versteeg, Almutairi, Hotez, & Pollet, 2019; Wykes, 2013). Different stages of the cycle can occur in the host as well. The parasite possibly has ways to sidestep immunity (heaven forbid) (Wykes, 2013).
Another possibility is loss of Memory B-Cells in the immune system over six – 12 months after an attack of Malaria. This means that vaccines based on antibodies might not be robust or long-lived. Some vaccines generate high amounts of antibodies in the blood and memory cells, but this does not last more than a few months. Some plasmodia weaken or alter the function of dendritic cells in the blood which are involved in generating long-term immunity (Versteeg et al., 2019; Wykes, 2013).
Lack of interest or a market for the vaccine, few companies manufacturing it. Malaria is a disease mainly occurring in impoverished countries. Major funding is required but there is extraordinarily
little investment return for pharmaceutical companies. Vaccines to date have been too expensive for many developing countries to purchase (Versteeg et al., 2019). This situation has the capacity to change.
Malaria has a high mortality rate and major damaging effects on individuals, families, communities and nations. Therefore, on malaria, prevention is essential by utilising a variety of strategies.
There is a new vaccine on the horizon
R21/Matrix-M, which was developed at Oxford University, and was tested on 450 children in Burkina Faso, between May and August, before the peak malaria season. The vaccine showed 77% efficacy at 12 months post vaccination follow-up. Antibody counts dropped much more rapidly with previous vaccines. Phase three trials are now underway in Burkina Faso, Kenya, Mali and Tanzania (Roxby, 2021). There is promise and hope.
Roxby, P. (2021). Malaria vaccine hailed as potential breakthrough [Press release]. Retrieved from https://www.bbc.com/news/health-56858158
Versteeg, L., Almutairi, M. M., Hotez, P. J., & Pollet, J. (2019). Enlisting the mRNA Vaccine Platform to Combat Parasitic Infections. Vaccines, 7(4). Retrieved from https://doi.org/10.3390/vaccines7040122
World Health Organization. (2021). ZEROING IN ON MALARIA ELIMINATION: Final report of the E-2020 initiative. 1-20.
Wykes, M. N. (2013). Why we haven’t made an efficacious vaccine for malaria. Retrieved from https://doi.org/10.1038/embor.2013.103