Written by Achi Kingsley

(Source: GAVI)

Outline 

• Malaria’s Impact on Africa
• Available Malaria Vaccine 
• Malaria Vaccine Implementation Program (MVIP)
• Prospects and Benefits for Africa
• Conclusion

Malaria’s Impact on Africa

Malaria is a tropical disease that is widely distributed in the African region. It is caused by five different species of malaria parasite which are transmitted by the female Anopheles mosquitoes. Plasmodium vivax and, especially, Plasmodium falciparum are the most prevalent and poses the greatest threat to Africans. In humans, the disease can be both life-threatening and fatal when left untreated. An estimated 247 million malaria cases and 619 000 deaths occurred globally in 2021 with sub–Saharan Africa having more than 95% of the burden. Africa experiences two primary seasons each year: dry and rainy seasons. According to a study, the transmission of P. falciparum, a malaria-causing parasite, thrives during the rainy seasons and seasons when temperatures range between 30-33°C. This correlation potentially clarifies why P. falciparum is more prevalent in African countries during climate conditions that align with these distinct seasons in the region. Adults from Africa survive the malaria infection more because have an acquired immunity against the infection. Unfortunately, this acquired immunity does not occur in children. WHO reported that children under 5 accounts for 80% of the malaria related death in Africa. Findings from a 2009 study revealed a reduction in the incidence of malaria cases and death among African children when immunity against P. falciparum was induced in them. This article discusses the malaria vaccine and its potentials effectiveness in the reduction of malaria burden in Africa. 

Available Malaria Vaccines 

Currently, only RTS,S/AS01 (RTS,S) and R21 /Matrix-M (R21) are the available malaria vaccines approved for public use. Researchers designed these vaccines to protect humans, especially children, against malaria infection. They used proteins from malaria parasite and the hepatitis B virus to produce this vaccine. These vaccines induce immune response and cause antibodies against plasmodium falciparum to be produced in the host’s body. The antibodies target the first lifecycle stage – sporozoite – of the parasite, just before it gets to the liver and spread throughout the body. The available vaccines have been tested and found to be safe and effective. Children between 5 months and 5 years of age are eligible to take the vaccine in a four-dose schedule, once per month, with an extra booster dose which may be given after one year, if necessary.

The two currently available malaria vaccines were developed independently by different research groups. Researchers from GlaxoSmithKhline (GSK), a UK based organization, developed the RTS,S/AS01 (RTS,S) malaria vaccine. It is the first vaccine that was successfully approved for programmatic use in October 2021 by WHO. The programmatic use of RTS,S vaccine was approved in three pilot African countries – Ghana, Malawi, and Kenya. As of now, an estimated two million children in Africa have been vaccinated with RTS,S. On the other hand, R21 /Matrix-M (R21) vaccine was developed by researchers from Oxford University and Serum Institute of India, and it is the second vaccine to be approved by WHO. The two available vaccines are similar. However, unlike the RTS,S,  the R21 vaccine contains higher proportion of the malaria parasite protein. This is because when there’s a higher proportion of the malaria antigen present, the immune system prioritizes targeting the malaria parasite over the component of the Hepatitis B Virus within the body.

(Source: GAVI)

Malaria Vaccine Implementation Program (MVIP)

The Malaria Vaccine Implementation Program (MVIP) was initiated by the World Health Organization (WHO) to pilot the RTS,S/AS01 malaria vaccine in routine immunization programs. This initiative aims to address specific objectives:

• Characterize the vaccine’s safety within routine immunization, focusing on safety signals observed in Phase 3 trials.
• Evaluate the vaccine’s effect on severe malaria and overall mortality.
• Assess the practicality of delivering the four-dose vaccine schedule within routine health services.

This program was designed to provide evidence to support broader malaria vaccine use in Africa. It involves collaboration between the following bodies: 

• World Health Organization 
• Ministries of Health in Kenya, Malawi, and Ghana
• International partners like PATH and UNICEF, including GSK that donated 18 million doses of the RTS,S malaria vaccine. 

Since 2019, over two million children under 5 years of age have been immunized against P. falciparum using the RTS,S vaccine. 

The vaccine is efficacious and safe. Result from the pilot program shows the following: 

• A 13% decline in mortality rate of malaria in children who received it. 
• Significant reduction in hospitalizations for severe malaria. 
• High malaria vaccine uptake with no significant reduction in the use of other prevention measure – like impregnated bed net. 

These results from the MVIP program have impacted the development and WHO recommendation of the second malaria vaccines, R21, to a great extent. Results from the phase 3 trial of R21 showed a good safety profile and reduced malaria in about 4800 children who were vaccinated in Burkina Faso, Kenya, Mali, and Tanzania. It is expected that R21, like RTS,S vaccine, will have high public health impact when rollout for use in a wider population. 

Vaccine to be used in any country will be based on the following: 

• Programmatic characteristics
• Vaccine supply 
• Affordability 

Although R21 vaccine has been approved for public use, WHO is currently reviewing it for prequalification. According to the WHO Regional Director for Africa, Dr Matshidiso Moeti, “This second vaccine holds real potential to close the huge demand-and-supply gap. Delivered to scale and rolled out widely, the two vaccines can help bolster malaria prevention and control efforts and save hundreds of thousands of young lives in Africa from this deadly disease.” 

Prospects and Benefits for Africa

The broad implementation of malaria vaccination in regions with moderate to high malaria risk will be a game changer, especially when done alongside other malaria control measures. 

The vaccines will benefit Africa in the following ways:

• In 18 high-risk countries, these vaccines, despite their shortcomings, show promise in lowering mortality rates, particularly among children. 
• The vaccines will be accessible and affordable to all, including the impoverished regions. 
• When combined with treatment and bed nets, these vaccines form a potent defense against the spread of malaria. 
• The recommendation of both vaccines signifies progress, hope, and resilience in the fight against malaria and the protection of African populations’ health.

Conclusion 

Malaria has plagued Africa for years, claiming the lives of thousands of young people annually. However, the advent of RTS,S/AS01 (RTS,S) and R21 /Matrix-M (R21) vaccines presents a beacon of hope in Africa’s fight against malaria, and results from the MVIP pilot program emphasizes the efficacy and safety of the vaccines. The pilot program will end by December 2023 and the shipment of available vaccines has begun with 331,200 doses landing Yaoundé, Cameroon in November 22, 2023. Shipment to 18 countries will continue with those countries not previously involved in the MVIP pilot program being prioritized. This marks a pivotal moment in Africa’s fight against malaria—a step closer to a healthier, more resilient future, free from the looming threat of this deadly disease.

References

Oxford University (2023). Oxford R21/Matrix-M™ malaria vaccine receives WHO recommendation for use paving the way for global roll-out. Available online: https://www.ox.ac.uk/news/2023-10-02-oxford-r21matrix-m-malaria-vaccine-receives-who-recommendation-use-paving-way-global

WHO World malaria report (2021) Available online: https://www.who.int/publications/i/item/9789240040496 (accessed: Jan 3, 2022)

Parham, P. E., & Michael, E. (2010). Modeling the effects of weather and climate change on malaria transmission. Environmental health perspectives, 118(5), 620-626.

Ngarakana-Gwasira, E. T., Bhunu, C. P., & Mashonjowa, E. (2014). Assessing the impact of temperature on malaria transmission dynamics. Afrika Matematika, 25, 1095-1112.

World Health Organization. (2021). Full evidence report on the RTS, S/AS01 malaria vaccine. SAGE Yellow B Oct, 2021, 1-90. https://cdn.who.int/media/docs/default-source/immunization/mvip/full-evidence-report-on-the-rtss-as01-malaria-vaccine-for-sage-mpag-(sept2021).pdf