* Modest reduction of 30 percent in malaria risk in babies
* Final-stage trial data leave vaccine's future in doubt
* GSK plans to push ahead with vaccine development
By Kate Kelland and Ben Hirschler
LONDON, Nov 9 A GlaxoSmithKline
experimental malaria vaccine touted as a new weapon in the fight
to eradicate the deadly disease proved only 30 percent effective
when given to African babies in a crucial clinical trial.
The surprisingly poor result leaves uncertain whether the
vaccine will have a useful role to play in fighting the
mosquito-borne disease that kills hundreds of thousands of
children a year.
Philanthropist Bill Gates, who has helped fund its
development, said further data was needed to determine whether
and how the vaccine might be used.
"The efficacy came back lower than we had hoped, but
developing a vaccine against a parasite is a very hard thing to
do," he said in a statement.
Results from the final-stage trial with 6,537 babies aged
six to 12 weeks showed the vaccine provided "modest protection",
reducing episodes of the disease by 30 percent compared to
immunisation with a control vaccine, researchers said on Friday.
That efficacy rate one year after vaccination is less than
half the 65 percent reported in a smaller mid-stage trial in
2008 that followed babies of a similar age for six months.
It is also a lot less than the 50 percent seen last year in
a large Phase III trial involving children aged five to 17
Vaccinating babies, rather than toddlers, is the preferred
option, since the new vaccine could then be added to other
routine infant immunisations. A separate programme for older
children would involve a lot of extra costs.
Despite the limited success, Britain's top drugmaker said it
would push ahead with developing the vaccine, called RTS,S or
Mosquirix, and Chief Executive Andrew Witty said he still
believed it would be an important tool in fighting malaria.
GSK does not expect to make any significant profit from the
vaccine, which would only be sold in poor countries.
Given the target market, it is governments and international
groups that will have to fund the vaccine's roll-out and they
will need more evidence before deciding that it is worth buying.
"We will have to have more information to give us a clearer
idea as to how useful this vaccine will be," said Seth Berkley,
CEO of the GAVI Alliance, which funds bulk-buy vaccination
programmes for poorer nations.
In particular, Berkley told Reuters he wanted to see
longer-term data, including the effect of booster shots, and an
analysis of how the vaccine performed in different settings,
which might show if it was suited for particular locations.
The setback comes two months after disappointing results
with a vaccine against dengue fever, another mosquito-borne
disease that is proving a formidable enemy.
Details of the malaria trial were presented at a medical
meeting in Cape Town and published online by the New England
Journal of Medicine.
Malaria is caused by a parasite carried in the saliva of
mosquitoes. It is endemic in more than 100 countries worldwide
and infected around 216 million people in 2010, killing around
655,000 of them, according to the World Health Organisation.
Control measures such as insecticide-treated bednets, indoor
spraying and the use of combination anti-malaria drugs have
helped cut the numbers of malaria cases and deaths significantly
in recent years, but experts say an effective vaccine is vital
to complete the fight against the disease.
The RTS,S vaccine is designed to kick in when the parasite
enters the human bloodstream. By stimulating an immune response,
it can prevent the parasite from maturing and multiplying in the
liver. Without that immune response, the parasite gets back into
the bloodstream and infects red blood cells, leading to fever,
body aches and in some cases death.
Other teams of scientists around the world are working on
other potential malaria vaccines which work in different ways,
but RTS,S is by far the furthest ahead in development.