Australian shot maker CSL Ltd. published results of a study that found between 75 percent and 96 percent 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 today confirm those findings, and show the protection starts rapidly, Dr. Anthony Fauci of the National Institutes of Health 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 center on adults; studies in children aren’t 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.

One dose means tight supplies of H1N1 vaccine won’t be stretched so badly after all.

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.