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 The analysis, published in the New England Journal of Medicine on
Wednesday, comes at a critical time for the experimental shot from
GlaxoSmithKline, when global experts are assessing how it might be
deployed.
GSK's Mosquirix, also known as RTS,S, is specifically designed for
use by African babies and toddlers. While it has the potential to
help prevent many cases of malaria, researchers have been
disappointed by its limited efficacy.
Hopes it could wipe out malaria were dampened when trial data in
2011 and 2012 showed it reduced episodes of the disease in babies
aged 6-12 weeks by only 27 percent, and by about 46 percent in
children aged 5-17 months.
Now scientists have discovered that genetic variability in a protein
found on the surface of malaria parasites may help explain the
patchy response because, while the protein comes in different forms,
GSK's vaccine incorporates only one variant.
The new study, funded by the U.S. National Institutes of Health,
looked at blood from 5,000 youngsters and found that the vaccine
gave less protection when toddlers were infected with parasites with
a different protein variant to the vaccine.
GSK said the research was interesting but early-stage.
"This single study is too small to offer conclusive evidence for how
RTS,S should be deployed," a spokeswoman said.
"However, the work underscores how a full and comprehensive catalog
of the genetic diversity of key pathogens could inform the design of
clinical studies in the future," she said.
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Experts advising the World Health Organization (WHO) have been
meeting in Geneva this week to draw up recommendations on how the
vaccine could be used. The U.N. agency, which normally follows such
advice, will make a recommendation by November.
Even if the WHO view is positive, the vaccine is unlikely to be
rolled out widely before 2017 since it still needs to win funding
from international donors and be approved by governments in the
African countries where it will be used.
GSK has said it will not make any profit from the vaccine, since it
will be priced at the cost of manufacture plus a five percent
margin, which will be reinvested in research on malaria and other
neglected tropical diseases.
(Editing by David Clarke)
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