DHAKA: Final clinical trials of a malaria vaccine - the first to reach this stage - suggest it could help protect millions of children against malaria.
But tests on 16,000 children from seven African countries found that booster doses were of limited use and vaccines in young babies were not effective, reports the BBC.
After children aged 5-17 months were given three doses of the vaccine, the immunisation was only 46 percent effective.
But experts say getting the vaccine this far is a scientific milestone.
Data from the trial published in The Lancet showed that the success rate fell to even lower levels in younger infants.
Scientists have been working on the vaccine for more than 20 years, but observers believe there is still a long way to go.
RTS,S/AS01 is the first malaria vaccine to reach advanced trials and show any sign of working in young children.
There is currently no licensed vaccine against malaria anywhere in the world.
With around 1,300 children dying in sub-Saharan Africa from malaria every day, scientists say they are delighted to have got to this stage in developing a vaccine against a very clever parasite.
BDST: 1029 HRS, APR 24, 2015