Nevertheless, this vaccine isn’t a “game changer”
Malaria is an infectious disease caused by a parasite called parasite P. falciparum. People can get malaria when they’re bitten by a mosquito that is infected with the parasite. People typically experience symptoms 10–15 days after being bitten by an infected mosquito. Initial symptoms may be mild, including headache and fever, and it can be hard to tell whether they indicate malaria. However, these symptoms can quickly become life threatening without treatment in the first 24 hours.
Each year, there are an estimated 200 million cases of malaria worldwide, with about 90% in sub-Saharan Africa. Nearly half of all 2017 malaria cases worldwide occurred in five countries: Nigeria, Democratic Republic of the Congo, Mozambique, India and Uganda. Around 400,000 people die every year from malaria, most of them children under 5 years old (67%). 94% of all malaria deaths (and cases) occur in Africa.
Until now, control measures for malaria were mostly things like draining stagnant pools of water to eliminate mosquito breeding places, introducing mosquito larvae eating fish into waters and encouraging the use of mosquito nets at night. All difficult interventions to do at scale especially in rural areas with poor infrastructure.
This week saw a hopeful new development- with an announcement by the World Health Organization that they recommend administration of a new vaccine that is safe and reasonably effective at preventing the worst effects from malaria infections.
This vaccine (called the RTS,S vaccine) was initially created in 1987 as part of a collaboration between GlaxoSmithKline (GSK) and the Walter Reed Army Institute of Research (WRAIR) that began in 1984. Oddly, pilot implementation in endemic countries until 2019 (I couldn’t find out why it took so long).
The Phase III clinical trial of the vaccine was picked up around 2001 with a public–private partnership with support from, you guessed it, the Bill and Melinda Gates Foundation. The vaccine’s effectiveness is modest, yet still provides significant public health benefit. The Phase 3 results demonstrated that among children who received 4 doses of vaccine, 1744 clinical malaria cases were prevented for every 1000 children vaccinated. Remember that this is a 4 dose series- challenging to do in rural high prevalence areas.
Modeling studies found that the vaccine would have marginal impact in areas where malaria prevalence is below 3%, and that the median incremental cost-effectiveness ratio is comparable to other current antimalarial interventions, including $25 USD per case averted and $87 USD per disability-adjusted life years averted, assuming $5 USD per dose of vaccine.
A description of the way the vaccine works is presented in this RTS,S/AS01 vaccine (Mosquirix™): an overview.
Editorial Note: This vaccine is an important development, representing the first vaccine against a parasite. The vaccine is moderately effective, but has a high return on investment public health wise in areas of high endemicity. The 4-dose series will be challenging to administer in rural areas where cases are highest. Finally, control measures like eliminating breeding places and protecting sleeping areas with nets and better access to treatment medications and hospitalization (when necessary) will continue to be critical in reducing morbidity and mortality from malaria- even in areas where the vaccine is deployed.
