Called Mosquirix, the new vaccine is given in three doses to
children between ages five and 17 months, and a fourth dose roughly 18 months
later. Following the clinical trials, the vaccine was tried out in three
countries
Malaria is among the oldest known and deadliest of
infectious diseases, killing about half a million people each year, nearly all
of them in sub-Saharan Africa and among them 260,000 children under age five.
The new vaccine, made by GlaxoSmithKline, rouses a child’s
immune system to thwart Plasmodium falciparum, the deadliest of five malaria
pathogens and the most prevalent in Africa.
The New York Times reported that the vaccine was not just a
first for malaria, but the first developed for any parasitic disease.
However, the report stated that in clinical trials, the
vaccine had an efficacy of about 50 per cent against severe malaria in the
first year, but dropped close to zero by the fourth year.
In addition, it stressed that the trials did not measure the
vaccine’s impact on preventing deaths, which has led some experts to question
whether it is a worthwhile investment in countries with countless other
intractable problems.
But severe malaria accounts for up to half of malaria deaths
and is considered “a reliable proximal indicator of mortality. I do expect we
will see that impact,” Dr. Mary Hamel, who leads the WHO’s malaria vaccine
implementation programme, said.
A modelling study last year had estimated that if the
vaccine were rolled out to countries with the highest incidence of malaria, it
could prevent 5.4 million cases and 23,000 deaths in children younger than age
five each year.
A recent trial of the vaccine in combination with preventive
drugs given to children during high-transmission seasons found that the dual
approach was much more effective at preventing severe disease, hospitalisation
and death than either method alone.
To have a malaria vaccine that is safe, moderately effective
and ready for distribution is “a historical event,” Director of WHO’s Global
Malaria Programme, Dr. Pedro Alonso said.
Parasites are much more complex than viruses or bacteria,
and the quest for a malaria vaccine has been underway for a hundred years, he
added, stressing, “It’s a huge jump from the science perspective to have a
first-generation vaccine against a human parasite.”
The malaria parasite is a particularly insidious enemy,
because it can strike the same person over and over.
In many parts of sub-Saharan Africa, even those where most
people sleep under insecticide-treated bed nets, children have on average six
malaria episodes a year.
Even when the disease is not fatal, the repeated assault on
their bodies can leave them weak and vulnerable to other pathogens, permanently
altering the immune system.
Malaria research is littered with vaccine candidates that
never made it past clinical trials. Bed nets, the most widespread preventive
measure, cut malaria deaths in children under age five by only about 20 per
cent.
Against that backdrop, the new vaccine, even with modest
efficacy, is the best new development in the fight against the disease in
decades, some experts said.
“Progress against malaria has really stalled over the last
five or six years, particularly in some of the hardest hit countries in the
world,” said Ashley Birkett, who heads malaria programmes at PATH, a non-profit
organisation focused on global health.
With the new vaccine, “there’s potential for very, very
significant impact there,” Birkett added.
Following the clinical trials, the vaccine was tried out in
three countries — Kenya, Malawi and Ghana — where it was incorporated into
routine immunisation programmes.
More than 2.3 million doses have been administered in those
countries, reaching more than 800,000 children. That bumped up the percentage
of children protected against malaria in some way to more than 90 per cent from
less than 70 per cent, Hamel said.
“The ability to reduce inequities in access to malaria
prevention — that’s important. It was impressive to see that this could reach
children who are currently not being protected,” Hamel added.
It took years to create an efficient system to distribute
insecticide-treated bed nets to families. By contrast, making Mosquirix a part
of routine immunisation made it surprisingly easy to distribute, he Hamel added
— even in the midst of the coronavirus pandemic, which prompted lockdowns and
disrupted supply chains.
“We aren’t going to have to spend a decade trying to figure
out how to get this to children,” he said.
This week, a working group of independent experts in
malaria, child health epidemiology and statistics, as well as the WHO’s vaccine
advisory group, met to review data from the pilot programmes and make their
formal recommendation to Director-General of the WHO, Dr. Tedros Ghebreyesus.
According to the NYT, the next step is for Gavi, the global
vaccine alliance, to determine that the vaccine is a worthwhile investment.
If the organisation’s board approves the vaccine — not
guaranteed, given the vaccine’s moderate efficacy and the many competing
priorities — Gavi will purchase the vaccine for countries that request it, a
process that is expected to take at least a year.
But as with COVID-19, problems with vaccine production and
supply could considerably delay progress and the pandemic has also diverted
resources and attention from other diseases, said Deepali Patel, who leads
malaria vaccine programmes at Gavi.
“COVID-19 is a big unknown in the room in terms of where
capacity is currently in countries, and rolling out COVID-19 vaccines is a huge
effort. We’re really going to have to see how the pandemic unfolds next year in
terms of when countries will be ready to pick up all of these other
priorities,” Patel said.
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