Fighting the swine flu may have gotten more manageable.

Australian and U.S. researchers said Thursday that one dose of the new swine flu vaccine looks strong enough to protect adults — and can begin protection within 10 days of the shot.

'This is quite good news.'— Dr. Anthony Fauci

Australian shot maker CSL Ltd. published results of a study that found 75 per cent to 96 per cent of vaccinated people should be protected with one dose — the same degree of effectiveness as the regular winter flu shot. That's remarkable considering scientists thought it would take two doses.

U.S. data to be released Friday confirm those findings and show the protection starts rapidly, Dr. Anthony Fauci of the National Institutes of Health told The Associated Press.

"This is quite good news," Fauci said.

The dose question has an important ramification: It means people will have to line up for influenza vaccinations twice this year instead of three times — once for the regular winter flu shot and a second time to be inoculated against swine flu, what doctors call the 2009 H1N1 strain.

Thursday's swine flu vaccine reports centre on adults; studies in children are not finished yet.

But scientists had feared that people of all ages would need two shots about a month apart because the new H1N1 strain is so genetically different from normally circulating flu strains that most of the population has little if any immunity.

Chinese manufacturers gave the first hint a week ago that one dose could be enough. But different manufacturers make different formulations of the vaccine, so more evidence was needed.

Dr. David Butler-Jones, Canada's chief medical officer of health, agreed the findings are promising. He cautioned, though, that it remains to be seen if one shot will work for teens and children, seniors and people with compromised immune systems.

The Public Health Agency of Canada is buying vaccine with adjuvant from vaccine giant GlaxoSmithKline, which has yet to release findings of its clinical trials. A clinical trial that will be used to license the GSK vaccine made for Canada will begin next week, Butler-Jones said.

Standard dose enough

Thus the CSL study, rushed out by the New England Journal of Medicine late Thursday, is welcome news. In a study of 240 adults, half younger than 50 and half over, one shot prompted the same kind of immune response indicating protection that is seen with regular flu vaccine. And a standard 15-microgram dose — not the double dose that also was tested — was enough.

CSL, which is one U.S. vaccine supplier, found the same side effects in its study that people experience with regular flu vaccine, which is no surprise since this shot is merely a recipe change from the annual standby. About 45 per cent of recipients had mild reactions such as a headache, sore arm or redness at the shot site.

On Friday, the NIH is set to release results of its own studies of hundreds of adults that confirm that one shot works, Fauci said. Plus, the U.S. work shows that people are protected eight to 10 days after that inoculation, he said.

Seasonal shots first

One dose means tight supplies of H1N1 vaccine won't be stretched so badly after all. The U.S. has ordered 195 million doses, based on the hope that 15 micrograms was indeed the right dose. Had it taken twice that dose, or two shots apiece, half as many people could have received the vaccine.

The winter flu vaccine is widely available now, and U.S. health authorities urged people to get it out of the way now before swine flu shots start arriving in mid-October.

Despite all the headlines about swine flu, which has become the main influenza strain circulating in the world, doctors do expect some garden-variety flu to hit this fall too — the kind that every year kills 36,000 Americans and hospitalizes 200,000.

"Take some individual responsibility to stay healthy during the flu season," said Health and Human Services Secretary Kathleen Sebelius, who scheduled her own seasonal shot for Friday.

Waiting to get the first inoculation out of the way "is not in anybody's best interest," added Dr. Nancy Nielsen, past president of the American Medical Association. She said busy doctors need to have completed regular vaccinations by the time they have to deal with H1N1 shots.

With files from The Canadian Press