Malaria is, in a word, awful.
And there’s a lot of it.
And the new vaccine for malaria is honestly meh. It’s safe, but its efficacy is nothing to sing about. That said, even a little improvement in malaria prevention multiplied by several hundred million people means a huge positive impact. The newly recommended vaccine for malaria is a landmark public health win–because small changes really matter at the population level.
Malaria: a life-threatening disease is caused by a microscopic parasite, which is transmitted by mosquito bite. When a person is bitten by an infected mosquito, the parasite infects the liver and then the red blood cells, where it produces a lot of toxic waste and makes people–lots and lots of people–very sick.
About 10-20 days after the mosquito bite, malaria symptoms appear and can include fever, shivering, chills, sweating, headache, nausea and vomiting, body aches, and fatigue. Severe cases can mean brain infection with symptoms like coma, seizures, and death; life-threatening anemia; respiratory collapse; organ failure; or several of these.
And it’s extremely common. Malaria infects more than 220,000,000 people every year worldwide. That’s 3 out of every 100 people in the world *every year*. It kills more than 250,000 kids under age 5 annually.
People who recover from malaria can get it again and again. In some places, children suffer from malaria as much as 4 times per year. Repeat malaria infection can lead to severe anemia, kidney disease, and immune system impairment. For example, a recent malaria infection will depress kids’ immune response to vaccines against other diseases, making them less effective.
As much as 93% of the world’s malaria happens in Sub-Saharan Africa, though it’s also endemic everywhere it’s warm and wet enough for the tropical mosquitoes that carry it: in the Mediterranean, Middle East, Indian Subcontinent, China, Southeast Asia, South America, Central America, and Mexico. And thanks to global climate change, the places where malaria isn’t are shrinking.
Researchers have been working toward a malaria vaccine for 50 years, but efforts have been slow. It’s a tough one to target with a vaccine. Malaria is a parasite, not a virus. It’s much more complex and sophisticated, and in particular it’s many-staged lifecycle is a vaccine challenge. Infection also produces weak immune memory, and the parasite can mutate rapidly–producing new strains that escape what immune memory there is. Also, global inequalities in resources and values have meant chronic low investment in research on a malaria vaccine.
But finally, a breakthrough.
Last week, a vaccine from GlaxoSmithKline called Mosquirix (also known as RTS,S) was recommended by the World Health Organization for certain high-risk populations: kids under age 5 living in Sub-Saharan Africa where the worst of the malaria parasite species is dominant: Plasmodium falciparum.
Mosquirix, like all vaccines, teaches the human adaptive immune system to recognize the thing that makes us sick in advance of actually meeting it. In this case, it targets the parasite during the part of its lifestage after the mosquito bite, but before it has infected the liver.
The efficacy of this vaccine is, in all honesty, not great. In the Phase 3 clinical trail, there were 39% fewer cases of clinical malaria in the treatment group compared to the placebo group, and it was worse (~30%) in a pilot program where nearly a million kids got the vaccine series. Compared to 97% efficacy of the measles vaccine, or even ~50% efficacy of the flu vaccine, it is a small effect. And efficacy drops off within a year of the last dose. And the series is 4 doses for children aged 6 weeks to 17 months, so it takes a good bit of coordination and parental commitment to deliver.
But even so, this vaccine’s introduction to high-risk areas will be an amazing public health win. Adding one more modest layer to existing malaria prevention efforts will have a big impact.
It’s a great example of how a small effect multiplied by a very large number of people can mean a lot. Malaria happens with such frequency in some places that this small additional protection is expected to add up to hundreds of thousands fewer cases every year, and tens of thousands of young lives saved.