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On Wednesday, the world marks World Mosquito Day to commemorate the 1897 discovery by British doctor Sir Ronald Ross that malaria in people is transmitted to and from mosquitoes. Ross won a Nobel prize for his discovery, and, since then, mosquitoes have been enemy No 1 when it comes to defeating a disease that takes a life every single minute – most of them children in sub-Saharan Africa.
But on this day, let’s focus on approaching malaria in a surprising new way: a vaccine to stop humans from giving malaria to mosquitoes.
If we can do this, we may finally stop malaria once and for all.
Why protect mosquitoes from humans? First, you have to understand the vicious cycle of malaria, which works like this: a mosquito bites a girl and transmits the malaria parasite, perhaps causing her to become very sick. A week later, a non-infected mosquito feeds on the same child, yet this time, it is the girl who passes the parasite to the mosquito. Soon, that mosquito – now carrying malaria parasites and buzzing around the same area – bites the girl’s father, passing the parasite to him. Even if he shows no symptoms of malaria and doesn’t get sick, he can still pass parasites on to another mosquito that in turn can transmit the parasite to another person, and so on.
That’s where a vaccine comes in.
A transmission-blocking vaccine (TBV) could break this often deadly cycle. This type of vaccine prevents the mosquito that bites the malaria-infected person from getting infected, thus stopping the parasite’s life cycle in its tracks. If the mosquito doesn’t get infected, it can’t give malaria to another person.
Of course, vaccinating humans to protect mosquitoes from malaria might sound a little crazy. From polio to smallpox, we think of vaccines as preventing people from getting a disease or from getting sick. This type of vaccine wouldn’t protect someone bitten by an infected mosquito from getting malaria or lessen its symptoms.
But what it would do is help protect that person’s family and community. And if almost everyone in a community received such a vaccine, over time the entire community would benefit from fewer and fewer infected mosquitoes flying around and, therefore, fewer malaria cases. Ultimately, this would create community immunity and eliminate malaria altogether from these areas. This long-term approach for the greater good – rather than immediate, personal protection – may seem novel, but the outcome would benefit us all: eradication of malaria.
Though we’ve made extraordinary progress over the past decade in reducing malaria deaths, the malaria parasite is rapidly becoming resistant to some of our best tools – drugs and insecticide sprays. Another tool to break the cycle of transmission could help tip the balance against malaria, and history tells us that a disease is unlikely to be eradicated without a vaccine.
To reach the end game, we need a suite of new tools that would work together – a suite that includes a vaccine.
There are potential transmission-blocking vaccines in early development. The nonprofit Path malaria vaccine initiative (MVI) is working with partners to research vaccine approaches. In collaboration with Fraunhofer USA Center for Molecular Biotechnology, we have advanced their transmission-blocking vaccine candidate through early-stage clinical trials, and the National Institutes of Health is also testing at least one vaccine approach in early-stage trials. The malaria vaccine technology roadmap, updated by the international community last year, has called for vaccines that reduce transmission by 2030 to help eradicate malaria.
Should a transmission-blocking vaccine become a reality, it would be another critical tool that paves the way for eliminating and eradicating malaria.
• Ashley Birkett is director of the Path MVI, a product development programme of the nonprofit, international global health organisation Path
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