Trials of a malaria vaccine in Africa have successfully protected babies from the disease, giving hope of cutting the global death toll of one million a year.
Most deaths from malaria are among babies, children under five and young women who become more vulnerable to the disease in pregnancy. There are 500 million cases every year, with many people becoming seriously ill. The toll is at its worst in Africa.
The vaccine, which is still known by its code name, RTS,S/AS02D, has already been shown to offer some protection to adult men and young children over the age of one. But the latest trial in Mozambique has shown that infants given the vaccine along with other routine immunisations in the early weeks of life are even better protected and suffer no serious side-effects.
The findings are important not only due to babies' vulnerability to malaria but also because their best chance of protection is a vaccine given within the routine childhood immunisation programme, which is relatively well-established in spite of the poor state of healthcare generally in Africa.
Pedro Alonso of the Hospital Clinic of the University of Barcelona, who led the trial, revealed that the vaccine had cut malaria cases by 65% among the babies in the trial.
Although the number of children involved was relatively small - 214, half of whom received the malaria vaccine - the result is significant because of the severity of the malaria problem in Ilha Josina and Taninga, 30 miles north of Manhica, Mozambique, where the trial was carried out. Those who did get malaria were less likely to become seriously ill - the number of cases needing clinical care was reduced by 35%.
"It is hard to overstate what a major step forward this is," said Ripley Ballou of GSK Bio, part of GlaxoSmithKline, which developed the vaccine in a public-private partnership with the Path Malaria Vaccine Initiative. Funding for the trial was provided by the Bill and Melinda Gates Foundation.
The families in the trial were all given the maximum possible amount of protection from malarial mosquito bites. They were supplied with insecticide-impregnated bed nets and trained how to use them, and the insides of their homes were sprayed with DDT, which is now government policy.
Even so, all these measures together with the vaccine did not prevent some cases. The researchers say in their paper, published online in the Lancet, that the vaccine must be seen as an additional weapon in the armoury against malaria and not a replacement.
"The future use and deployment of a malaria vaccine should be seen in the context of comprehensive malaria control programmes," they write.
None the less, they say, they have definitely shown that babies exposed to intense malaria transmission in Africa can be protected by a vaccine. "These results further strengthen the vision that a vaccine that can partly protect young African children and infants might contribute to the reduction of the intolerable burden of disease and death caused by malaria."
The findings were announced at a meeting of experts, scientists and government officials convened yesterday by the Gates Foundation in Seattle to review progress in the battle against malaria.
Mr and Mrs Gates called on government leaders to embrace "an audacious goal - to reach a day when no human being has malaria and no mosquito on earth is carrying it".
The next step will be a phase 3 trial, involving 16,000 children in seven countries, which will start towards the end of next year and last for two years. If that is also successful, GSK will seek a licence in the hope that it can be rolled out swiftly across Africa's malaria belt, where most deaths occur every year.