Good news in the world's flu fight: One dose of the new swine flu vaccine looks strong enough to protect adults — and can spark protection within 10 days of the shot, Australian and US researchers said Thursday. 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. US 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. 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. 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. 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 was enough. About 45 percent of recipients had mild reactions such as a headache, sore arm or redness at the shot site. One dose means tight supplies of H1N1 vaccine won't be stretched so badly after all. The winter flu vaccine is widely available now, and US health authorities urged people Thursday to get it out of the way now before swine flu shots start arriving in mid-October. Despite all the headlines about swine flu, doctors do expect some garden-variety flu to hit this fall too. There's no way to predict how much of either flu strain will circulate. A separate report in Thursday's New England Journal suggested European manufacturers might get away with an even smaller dose. Novartis Vaccines added what's called an adjuvant, or immune-boosting chemical, to its version of the swine flu shot and found a 7.5-microgram dose was effective. It did, however, spark more of those reactions like injection-site pain.
