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The world has acquired a new weapon in the war against malaria, one of the oldest and deadliest infectious diseases known: the first vaccine proven to help prevent disease. According to one estimate, it will save tens of thousands of children every year.
Malaria kills around half a million people each year, almost all of them in sub-Saharan Africa, including 260,000 children under the age of five. The new vaccine, made by GlaxoSmithKline, stimulates a child’s immune system to thwart Plasmodium falciparum, the deadliest of the five malaria pathogens and the most common in Africa.
The World Health Organization on Wednesday approved the vaccine, the first step in a process that is expected to lead to wide distribution in poor countries. Having a safe, moderately effective and ready-to-distribute malaria vaccine is “a historic event,” said Dr Pedro Alonso, director of the WHO Global Malaria Program.
Malaria is rare in the developed world. There are only 2,000 cases in the United States each year, mostly among travelers returning from countries where the disease is endemic.
The vaccine, called Mosquirix, is not just a first for malaria – it is the first developed for any parasitic disease. Parasites are much more complex than viruses or bacteria, and the quest for a vaccine against malaria has been underway for a hundred years.
“It’s a huge leap from a scientific point of view to have a first generation vaccine against a human parasite,” said Dr Alonso.
In clinical trials, the vaccine has had a efficiency of about 50 percent against severe malaria in the first year, but the figure fell to almost zero by the fourth year. And the trials did not directly measure the vaccine’s impact on deaths, leading some experts to wonder if it is worth it investments in countries facing countless other intractable problems.
But severe malaria accounts for up to half of malaria deaths and is considered “a reliable proximal indicator of mortality,” said Dr Mary Hamel, who leads the WHO malaria vaccine implementation program. “I expect we will see this impact.”
A modeling study last year estimated that if the vaccine were rolled out in countries with the highest incidence of malaria, it could prevent 5.4 million cases and 23,000 deaths in children under 5 years of age each year.
A recent trial of the vaccine in combination with preventative drugs given to children during seasons of high transmission found that the dual approach was much more efficient to prevent serious illness, hospitalization and death than either method alone.
The malaria parasite, carried by mosquitoes, is a particularly insidious enemy because it can strike the same person over and over again. In many parts of sub-Saharan Africa, even where most people sleep under insecticide-treated mosquito nets, children have an average of six episodes of malaria per year.
Even when the disease is not fatal, repeated assaults on their bodies can permanently alter the immune system, leaving them weak and vulnerable to other pathogens.
Malaria research is full of vaccine candidates that have never made it past clinical trials. Bednets, the most widely used preventive measure, have reduced malaria deaths in children under 5 by only about 20 percent.
Against this background, the new vaccine, even with modest efficacy, is the best new development in the fight against the disease in decades, some experts have said.
“Progress against malaria has really stalled over the past five or six years, especially in some of the hardest-hit countries in the world,” said Ashley Birkett, who heads malaria programs at PATH, a non-profit organization focused on global health.
With the new vaccine, “there’s a very, very big impact potential out there,” Dr Birkett said.
Mosquirix is given in three doses between 5 and 17 months, and a fourth dose about 18 months later. Following clinical trials, the vaccine has been tested in three countries – Kenya, Malawi and Ghana – where it has been incorporated into routine immunization programs.
Over 2.3 million doses have been administered in these countries, affecting over 800,000 children. This has pushed up the percentage of children protected against malaria in one way or another to over 90 percent, from less than 70 percent, Dr Hamel said.
“The ability to reduce inequalities in access to malaria prevention – this is important,” said Dr Hamel. “It was impressive to see that it could affect children who are currently unprotected.”
It took years to create an effective system of distributing insecticide-treated bednets to families. In contrast, the inclusion of Mosquirix among routine vaccinations made its distribution surprisingly easy, added Dr Hamel – even amid the coronavirus pandemic, which has caused lockdowns and disrupted supply chains.
“We’re not going to have to spend a decade trying to figure out how to pass this on to children,” he said.
This week, an independent expert working group on malaria, epidemiology and child health statistics, as well as the WHO advisory group on vaccines, met to review data from the pilot programs and make their formal recommendation to Dr Tedros Adhanom Ghebreyesus, Director-General of WHO
“We still have a very long way to go, but it is a long step on this road,” Dr Tedros said at a press conference on Wednesday.
The next step is for Gavi, the global vaccine alliance, to determine that the vaccine is a worthwhile investment. If the organization’s board of directors approves the vaccine – which is not guaranteed, given the vaccine’s moderate efficacy and many competing priorities – Gavi will purchase the vaccine for countries that request it, a process which should take at least a year.
But as with Covid-19, problems with vaccine production and supply could significantly delay progress. And the pandemic has also diverted resources and attention from other diseases, said Deepali Patel, who heads malaria vaccination programs at Gavi.
“Covid is a big unknown in the room in terms of current capacity in countries, and the deployment of Covid-19 vaccines is a huge effort,” Ms. Patel said. “We’re really going to have to see how the pandemic plays out over the next year to see when countries are ready to pick up on all of these other priorities. “
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