It’s taken decades of development and cost hundreds of
millions of dollars to fund, but the results are finally in for the
first malaria vaccine ever to have reached phase 3 trials.
Tested on thousands of infants and children across seven sub-Saharan
countries, the RTS,S vaccine “prevented a substantial number of cases”
of malaria over the four-year trial period. It was found to be most
effective against malaria among children compared with young infants.
Using randomized trials, and funded by GlaxoSmithKline (GSK) and the PATH Malaria Vaccine Initiative,
the researchers enrolled over 15,000 infants and children. After 18
months, the number of clinical cases of malaria—those cases confirmed by
a doctor—was reduced by 46% amongst children and by around 27% in young
infants. But the protection offered by the vaccine waned over time,
despite some being given booster shots.

Amongst those who received the three doses of RTS,S plus a booster
shot, the number of cases of clinical malaria four years later was
reduced by just over a third (36%), a drop in effectiveness from the 50%
seen in the first year. The RTS,S vaccine and booster shot were
slightly less effective in young infants, providing them with no
statistically significant protection against the disease.
A reduction of infection by only a third might not seem like much of a success, but as Brian Greenwood,
corresponding author and professor of clinical tropical medicine at the
London School of Hygiene and Tropical Medicine, explains, "Given that
there were an estimated 198 million malaria cases in 2013, this level of
efficacy potentially translates into millions of cases of malaria in
children being prevented."
The study, published in The Lancet,
reported that over three years of follow-up, an average of 558 cases of
malaria were averted for every 1,000 infants vaccinated. Among those
also given the booster dose, an average of 983 additional cases were
prevented. With over half a million deaths caused by malaria every year
in Africa alone, the figures soon stack up.
"We finally have in our sights a candidate vaccine that could have a
real impact on this terrible disease that affects many children during
their first years of life," said Dr. Kwaku Poku Asante,
a principle investigator in the RTS,S trial. "The large number of
children affected by malaria, sometimes several times per year, means
that this vaccine candidate, if deployed correctly, has the potential to
prevent millions of cases of malaria."
The vaccine specifically targets the Plasmodium falciparum
species of malaria, which is the most dangerous and prevalent form in
sub-Saharan Africa, killing around 1,300 children a day. Made from
proteins found on the parasite's surface, the vaccine works by
encouraging the patients' own immune system to attack the malaria before
it is able to enter the liver where it can mature.
There is currently no licensed vaccine against malaria anywhere in the world, and the researchers are now waiting on the European Medicines Agency (EMA) to analyze the data from the trial. If they give it a favorable review, the World Health Organization
could recommend the use of RTS,S by as early as this October, and the
vaccine could then be rolled out through African national immunization
programs. If approved, GSK has committed to making the vaccine available
at a not-for-profit price.
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