Every year in sub-Saharan Africa, parents have to bury 250,000 children under the age of 5 — because of deadly mosquito bites. It has been difficult to put this number in perspective before the COVID-19 pandemic and its massive death toll, and it has been even harder to watch this play out on the ground.
Now, finally, we have a vaccine that, even with 40 percent efficacy, can put a dent in malaria’s horrible death toll. Even with the excitement around this news, the malaria vaccine is not a perfect vaccine. We have found that the COVID-19 vaccine, and its remarkable efficacy that needed only a year for development, has raised expectations well beyond what was once reasonable. But four doses of this new malaria vaccine will likely save tens of thousands of lives around the world. As with all diseases, we want the most efficacy in our vaccines, but better disease prevention is not available right now.
A closer look at the unique aspects of malaria can be instructive. Malaria is caused by parasites transmitted by the bite of female Anopheles mosquitoes. Most deaths are due to infection with one parasite in particular — Plasmodium falciparum. For more than two decades now, we have been working with Zambian colleagues on understanding disease transmission and control.
In the country’s northern regions, malaria accounts for more than one third of all pediatric hospitalizations and almost 40 percent of all hospital deaths in children. There, the biting mosquitoes are exceptionally efficient at delivering malaria, with most people exposed to the microscopic parasite causing the disease at least once every two or three days throughout the year.
Repeated infections can result in some protection against severe disease, but surviving to adulthood is not guaranteed. Young children, without such immunity, are at risk of severe, debilitating disease and death, often due to anemia or brain infections. If they survive, many will be impaired for life.
Since the origin of malaria was discovered, we have developed public health strategies to control the disease. We have deployed bed nets and insecticides to reduce the abundance of biting mosquitoes. We have also developed antimalarial drugs to eliminate the parasite from infected individuals. Improved living conditions in many wealthier countries also prevent mosquitoes from entering and infecting the occupants — but these advancements haven’t always reached the more impoverished communities.
The prevention strategies have generated some great advances and 40 countries — including El Salvador in 2020 and China in 2021 — have been certified by the World Health Organization (WHO) to have eliminated malaria. However, in many other countries — mostly the less wealthy ones — progress in reducing the burden of malaria has stalled or even reversed.
In the field, we see that mosquitos are acquiring insecticide resistance, ignoring the chemical barriers set up to restrict biting. The malaria parasites are acquiring resistance to some of our strongest medicines, including the gold standard for treatment over the past decade and a half — artemisinin combination therapy. We urgently need new tools in our toolbox to fix this tragic disease burden. And that is where the imperfect vaccine fits in.
The COVID-19 vaccines, which have so safely and effectively reduced hospitalizations and deaths, address a virus that has perhaps a dozen genes, while a malaria parasite has more than 5,000 genes. Up until now, any vaccine for malaria has been elusive despite decades of research — but the same scientific breakthroughs that helped generate the COVID-19 vaccines can now be harnessed to generate a more perfect vaccine. Researchers are currently evaluating a number of promising compounds in various stages of clinical trials. Until these are proven effective, however, we will need to deploy what we have to stem this terrible disease.
Malaria, like COVID-19, will not disappear tomorrow. Better vaccines are needed that provide better protection with fewer doses, along with new tools to ward off mosquitoes and new medicines to treat drug-resistant infections. We also need better ways to deliver medicines — and now, this vaccine — to rural communities.
The war is far from over, but there is now more hope for survival and a glimpse, finally, of better days ahead.
Peter Agre, MD, a Nobel laureate in 2003, is the director of the Johns Hopkins Malaria Research Institute. William J. Moss, MD, MPH, is the executive director of the International Vaccine Access Center at the Johns Hopkins Bloomberg School of Public Health.