Latest NewsMalaria StoriesThe new malaria vaccine might not be perfect, but it will save countless lives

March 15, 2022by ammren_admin

In 2020 malaria sickened 241 million people and killed roughly 627,000. In sub-Saharan Africa, where 95% of cases and deaths took place, children under five accounted for 80% of the fatalities.

The numbers are horrifying—but there is finally a reason for optimism. Last October, the World Health Organization approved GlaxoSmithKline’s malaria vaccine, known as RTS,S or Mosquirix. It’s the world’s first vaccine for the deadly disease, which is spread to people through the bites of female Anopheles mosquitoes infected with the Plasmodium parasite. Meanwhile, BioNTech, the German biotech company that teamed with Pfizer to develop a covid-19 vaccine based on mRNA, is aiming to begin clinical trials of a malaria vaccine in 2022. The tide may finally be turning.

The WHO’s approval paves the way for a massive rollout of Mosquirix across Africa. It’s also the first vaccine for any type of parasite, marking a watershed in the fight against not just malaria but scores of other tropical diseases. By some estimates, more than 2 billion people are currently infected with parasitic worms. And though treatments exist for many of the cases, microbiologists have been trying in vain for years to develop vaccines that would prevent infection or reinfection. The success of the malaria vaccine proves it’s possible.

Parasites, tiny multicelled animals, have genomes 500 to 1,000 times larger than those of most viruses and single-celled pathogens. This allows them to mutate in myriad ways when challenged by an immune response. Malaria, in particular, is a master of disguise. In the later stages of its life cycle, it can display any one of 60 different proteins on its surface, switching them up as needed to evade the immune system’s detection.

“We’re basically dealing with evolution’s greatest hit—these things know us better than we know ourselves,” says Photini Sinnis, deputy director of the Johns Hopkins Malaria Research Institute. “They have figured out how to do what they need to do. And they have a large enough genome that they can really manipulate our immune system so that they can succeed in living in us.”

In fact, the new malaria vaccine, which has been in testing since 1987, is not particularly effective. In a pilot implementation involving more than 800,000 children in Kenya, Malawi, and Ghana, it had an efficacy of just 50% in preventing severe malaria in the first year, and its effectiveness dropped dramatically over time. (By contrast a three-dose regimen of the polio vaccine is 99% effective in preventing infection.) It is relatively impotent once the parasite has established a foothold in the body’s blood cells, so the vaccine must neutralize it soon after infection.

Still, scientists believe they have found a regimen that will make its use worthwhile. It requires three doses between the ages of five months and 17 months, and a fourth dose given 12 to 15 months after the third dose. One clinical trial showed that when combined with existing malaria control measures, which include insecticide-­treated bed nets and preventative drugs administered during rainy season, the regimen could reduce malaria deaths by around 70%, compared with children who had only received existing preventative drugs.

“It’s going to save lives,” says Dyann Wirth, an immunologist at Harvard’s school of public health and an expert on malaria. “And it will spur the research community and the funders who are needed for the research community to actually continue to innovate.”

Strange brew

For decades, vaccinations typically worked by exposing people to a weak or inactivated version of a pathogen—one strong enough to ring alarm bells in the immune system and cause the body to build defenses against it, but not strong enough to make someone sick.

Early efforts to take this approach with the malaria parasite were hampered by the difficulty of growing the parasite in a lab and a number of other logistical problems, says Sinnis. In the 1980s researchers began to explore what was then a wholly new approach to a malaria vaccine—one that wouldn’t need the whole parasite but just a small portion of it.

Scientists first identified the proteins present on the malaria parasite’s surface right after it enters the human body—targets that the immune system could recognize and attack. In order to enhance the immune response, they discovered, it would be necessary to add additional ingredients.

Choosing these extra immune-stimulating components, known as adjuvants, and merging them with the malaria proteins constituted a scientific challenge. To guard against autoimmune diseases and even allergies, some immunologists suggest, the human immune system has multiple safety mechanisms aimed at preventing it from needlessly attacking irrelevant or harmless proteins.

CREDIT: https://www.technologyreview.com