Scientists have been working on a vaccine against malaria — an infectious disease spread by mosquitoes that infects over 230 million people annually and kills 400,000, most of whom are children — since the 1980s. More than thirty years in the making, the first malaria vaccine has finally passed its Phase III clinical trials in three African countries and the World Health Organization (WHO) now recommends its approval.
A lifesaver for children worldwide
The vaccine, known as RTS,S (trade name Mosquirix), was developed by GlaxoSmithKline. It started its first pilot immunization program in Ghana, Kenya, and Malawi where it was found to prevent approximately 4 in 10 malaria cases, including 3 in 10 cases of life-threatening severe malaria. Furthermore, the vaccine also cut the level of severe anemia—the most common reason kids die from the disease—by 60%.
The Mosquirix vaccine is given in three doses between the ages of 5 months and 17 months, with a fourth dose about 18 months later. The most recently closed clinical trials have shown Mosquirix is 50% effective against severe malaria in the first year. However, the vaccine-granted immunity wanes with time, its efficacy plummeting close to zero by the fourth year.
After these clinical trials, the vaccine coverage was expanded to include more than 800,000 children who have received 2.3 million doses of the vaccine thus far. This program showed that the vaccine was 40% effective in the ‘real world’.
If the vaccine was rolled out extensively in countries with the highest incidence of malaria, 5.4 million cases and 23,000 deaths among children younger than 5 years could be prevented annually, according to a modeling study from 2020.
According to Kate O’Brien, the Director of WHO’s Department of Immunization, Vaccines, and Biologicals, young infants are at the highest risk of severe outcomes, and so having a vaccine that can prevent disease in children and infants would be a groundbreaking new strategy.
“This is a historic moment. The long-awaited malaria vaccine for children is a breakthrough for science, child health and malaria control,” said WHO Director-General Dr. Tedros Adhanom Ghebreyesus in a statement. “Using this vaccine on top of existing tools to prevent malaria could save tens of thousands of young lives each year.”
Malaria: a hard nut to crack
Although tremendous advances have been made against malaria over the last two decades thanks to prevention and control measures, such as insecticide-treated bed nets, indoor spraying with insecticides, and the timely use of malaria testing and treatment, progress has stalled or even reversed in some areas. The long-awaited vaccine was the missing puzzle piece that health workers were looking for in their long war against malaria.
Malaria is transmitted through the bite of a mosquito that was infected with the Plasmodium parasite. Symptoms include fever, chills, headache, anemia, convulsions, and sweating. A single bite from a malaria-infected mosquito will cause several bouts of the disease, which means a lot of missed school and progressively poorer health during formative years.
There are over 100 different malaria-causing parasites, but Mosquirix only targets one, which is the most common and deadly in Africa: Plasmodium falciparum.
While the COVID mRNA vaccines were designed in a matter of days and immediately started clinical trials, the malaria vaccine took decades to mature. The huge discrepancy is owed to the malaria parasite’s much more sophisticated nature than the coronavirus. Plasmodium parasites have evolved to evade our immune system, being able to hide in the host’s liver and emerge many times over a period of years. To gain natural immunity, you have to be infected multiple times with the parasite. During some of these infections, you risk death. You could say we’ve been lucky that the pandemic is a coronavirus one and not a Plasmodium one.
“From a scientific perspective, this is a massive breakthrough, from a public health perspective this is a historical feat,” said Dr. Pedro Alonso, the director of the WHO Global Malaria Programme.
“We’ve been looking for a malaria vaccine for over 100 years now, it will save lives and prevent disease in African children.”
Malaria vaccines could prove even better in the future. The Jenner Institute at the University of Oxford developed a vaccine against malaria that was shown to be 77% effective in trials in Africa, earlier this year.