By Denise Roland
LONDON-- GlaxoSmithKline PLC's malaria vaccine, the world's most
advanced, loses effectiveness over time, even with a booster shot,
according to clinical-trial results published on Friday.
Nonetheless, the scientists who conducted the study said the
vaccine still offered a clear benefit to children in sub-Saharan
Africa, where the disease is widespread.
Earlier results showed that young children who received three
doses of the vaccine in close succession were half as likely to
contract malaria in the year following the shots. But a follow-on
study published Friday in the Lancet, a medical-research journal,
showed that after four years the level of protection dropped to
just 36%, despite a fourth dose being given at the 18-month
mark.
The effect in infants was weaker still. Babies given the first
three shots aged between six and 12 weeks, and a booster later on,
were just 26% less likely to contract malaria after three years.
They weren't followed up for four years.
The vaccine was also shown to be less effective against severe
malaria, the life-threatening form of the disease. Without a
booster, neither infants nor young children were protected from
this form of the disease after three and four years, respectively.
Using the booster made young children 32% less likely to contract
severe malaria but made no difference to infants.
The latest results are the final part of a five-year trial on
more than 15,000 children across 11 African countries.
Brian Greenwood, professor of clinical tropical medicine at the
London School of Hygiene and Tropical Medicine, and one of the
scientists involved in the study, said that, despite falling
efficacy over time, the vaccine still marked a clear improvement
over the status quo.
"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," he said.
The Glaxo vaccine is the most advanced inoculation anywhere in
the world by at least 10 years. Malaria is notoriously difficult to
vaccinate against because the disease is caused by a complex
parasite, and it has taken the British drug company nearly three
decades to reach this point. Glaxo has said it plans to sell the
vaccine at a 5% premium to the manufacturing cost and use the
profits to fund further research into vaccines for malaria and
other neglected tropical diseases.
Dr. Moncef Slaoui, chairman of global vaccines at Glaxo, said he
was "extremely encouraged" by the results. He added: "We might
reasonably now expect that the impact of this vaccine candidate,
when used with existing interventions, will allow more children to
survive the early years which we know is the most dangerous time to
be infected with malaria."
Glaxo has already submitted the vaccine to European regulators,
based on earlier data, and hopes that the shot could launch as
early as next year. The World Health Organization has already
indicated that it will recommend the vaccine should it win
regulatory approval.
However, WHO officials, also writing in the Lancet, stressed
that the vaccine must be funded in such a way as to preserve
financial support for other strategies to decrease the spread of
the disease, such as the provision of mosquito nets and
antimalarial drugs.
Write to Denise Roland at Denise.Roland@wsj.com
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