Dr Tom Beddis / The Adventure Medic
On October 6th the WHO announced new recommendations for the widespread use of the Malaria vaccine RTS, S in sub-Saharan Africa1. This is on the back of a successful pilot roll out in Malawi, Ghana, and Kenya which has administered over 800,000 doses of vaccine to children in Africa since 2019. This news adds to an already exciting year for the fight against Malaria with a potentially even more effective vaccine entering phase three trials earlier this year.
Why has it taken so long to develop an effective vaccine?
You may be wondering why, if in the space of a year scientists have been able to develop COVID-19 vaccines, has it taken so long to develop a malaria vaccine? Whilst malaria has not had the same level of international interest and funding, the main reason is how technically difficult it has been due to the complex life cycle of Plasmodium and its high mutation rate.
How does the vaccine work?
The RTS, S vaccine (also called Mosquirix) was the first ever licensed vaccine against a human parasitic disease. It consists of two parts. The first is a recombinant protein which is normally secreted by the Plasmodium parasite during its sporozoite phase; this is the phase in which the parasite enters the human body from the mosquito. This protein is then combined with the surface antigen of the hepatitis B virus (HBsAg) to form a soluble, virus-like particle2. The second part of the vaccine is an adjuvant chemical which helps to boost the immune response.
How has the vaccine been used so far?
The vaccine was first approved by the European Medicines Authority in 2015 after being shown in clinical trials to be up to 56% effective in preventing Malaria at one year3. In 2019 the WHO introduced a pilot implementation of RTS, S in Malawi, Ghana and Kenya which offered the vaccine to children up to the age of 2 years.
The future?
The future is looking positive in the fight against Malaria. The WHO is now recommending the widespread use of the vaccine across Africa with the potential to save hundreds of thousands of lives. Not only this but other vaccines are in development that hope to provide even more effective protection. For example, the R21 vaccine that showed an even higher 77% efficacy at one year in phase 2 trials in Burkina Faso, has now entered phase 3 testing4,5.
You can find out more about the WHO Malaria Vaccine Implementation Programme here.
References
1. WHO recommends groundbreaking malaria vaccine for children at risk [Internet]. Who.int. 2021 [cited 11 October 2021]. Available from:https://www.who.int/news/item/06-10-2021-who-recommends-groundbreaking-malaria-vaccine-for-children-at-risk
2. HEPPNERJR D, KESTER K, OCKENHOUSE C, TORNIEPORTH N, OFORI O, LYON J et al. Towards an RTS,S-based, multi-stage, multi-antigen vaccine against falciparum malaria: progress at the Walter Reed Army Institute of Research. Vaccine. 2005;23(17-18):2243-2250.
3. Efficacy and safety of RTS,S/AS01 malaria vaccine with or without a booster dose in infants and children in Africa: final results of a phase 3, individually randomised, controlled trial. The Lancet. 2015;386(9988):31-45.
4. Datoo M, Natama M, Somé A, Traoré O, Rouamba T, Bellamy D et al. Efficacy of a low-dose candidate malaria vaccine, R21 in adjuvant Matrix-M, with seasonal administration to children in Burkina Faso: a randomised controlled trial. The Lancet. 2021;397(10287):1809-1818.
5. Promising malaria vaccine enters final stage of clinical testing in West Africa | University of Oxford [Internet]. Ox.ac.uk. 2021 [cited 11 October 2021]. Available from:https://www.ox.ac.uk/news/2021-05-07-promising-malaria-vaccine-enters-final-stage-clinical-testing-west-africa
