The U.S. National Institutes of Health says clinical trials show that
the new H1N1 swine influenza vaccine could protect against the virus
with just one dose instead of two as had previously been expected.
This means vaccine supplies could be available for twice as many people.
Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, says trials show that adults who got a single dose of the swine flu vaccine were protected from the virus within eight to 10 days.
Fauci is expected to officially release the U.S. vaccine trial results at a news conference Friday.
On Thursday, the New England Journal of Medicine published two studies that also confirmed a single vaccination could protect against the virus.
Australian vaccine maker CSL Limited and Swiss Drug company Novartis conducted the studies.
Also Friday, the World Health Organization released new advice for schools to reduce the spread of swine flu.
The WHO said schools deciding to close because of an H1N1 outbreak should do so at an early stage to slow transmission of the virus.
The WHO has declared the swine flu outbreak a pandemic, and says up to two billion people may eventually be infected. It says more than 3,000 deaths related to the virus have been reported worldwide.
Some information for this report was provided by AFP, AP and Reuters.