The world's first potential malaria vaccine proved only 30% effective in African babies in a crucial phase III trial, calling into question whether it can be a useful weapon in the fight against the deadly disease.
The surprisingly poor result for the vaccine, which GlaxoSmithKline has been developing for three decades, leaves several years of work ahead before a protective malaria shot could be ready for countries that desperately need one.
Philanthropist Bill Gates, who helped fund the GSK vaccine's development, said further research was now needed to see whether and how it 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.
How the study was done
In the study of 6 537 babies aged six to 12 weeks, the vaccine provided "modest protection," reducing episodes of the disease by 30% compared to immunisation with a control vaccine, researchers said.
That efficacy rate a year after vaccination is less than half the 65% in an earlier trial in babies that analysed protection rates after six months. It is also a lot less than the 50% seen in 5- to 17-month-olds.
Vaccinating babies, rather than toddlers, is the preferred option, since the new vaccine could then be added to other routine infant immunizations. A separate program for older children would involve a lot of extra costs.
Eleanor Riley, a professor of immunology at the London School of Hygiene and Tropical Medicine said the results showed that GSK's vaccine, called RTS,S or Mosquirix, is potentially useful, but "not the complete solution".
"The slightly lower than expected efficacy will ... affect the cost-benefit analysis that health providers and funders will have to undertake before deciding whether the vaccine represents the best use of limited financial resources," she said.
More positive data needed
Despite the setback, Britain's top drug maker said it would push ahead with developing RTS,S and GSK Chief Executive Andrew Witty said it could be an important tool in fighting malaria.
"We've been at this for 30 years, and we're certainly not going to give up now," he told reporters on a conference call.
GSK does not expect to make any profit from the vaccine, which would only be sold in poor countries.
Witty reiterated a promise that if RTS,S is ultimately approved for market, it would be priced at cost of manufacture plus a 5% margin, and the margin would be reinvested by GSK in malaria research.
Given the target market, it is governments and international groups that will fund the vaccine's roll-out, and they now need more positive data before deciding whether 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 said he wanted to see longer-term data, including the effect of booster shots, and an analysis of how the vaccine performed in different settings.
Details of the malaria trial, which is Africa's largest ever clinical trial involving almost 15 500 children in seven countries, were presented at the International African Vaccinology Conference in Cape Town.
Witty said he would have liked to have seen efficacy rates of around 50% in infants, but stressed that more data would become available before the trial ends in 2014 which may throw more light on why rates of success are so variable.
"It may open up a more customised approach to how this potential vaccine gets used," he said.
(Reuters Health, November 2012)
GSK malaria vaccine long-lasting protection