Study questions U.S. flu vaccine guidelines

CHICAGO (Reuters) - Contrary to current U.S. strategy, vaccinating school children and their parents against the flu is the best way to protect the nation from influenza, including the new pandemic swine flu, U.S. researchers said on Thursday.

They said vaccine priority should be given to people most likely to spread the virus, not those most at risk of serious complications from it.

Seasonal and H1N1 vaccination guidelines from the U.S. Centers for Disease Control and Prevention currently target people who are likely to become the most ill if infected.

"The vaccines would be better used to prevent transmission within schools and out to parents, who then spread the flu to the rest of the population," said Jan Medlock of Clemson University in South Carolina, whose study appears in the journal Science.

Medlock and colleague Alison Galvani of Yale University in New Haven, Connecticut, developed a mathematical model of flu spread that takes age and transmission patterns into account.

They said a vaccine strategy focused on children 5 to 19 and adults 30 to 39 -- who most often get the flu from their children -- emerged as the most effective way to halt the spread of disease.

Such an approach could stop the spread of a flu with just 63 million doses of vaccine, they said. "If you can stop it in the schools, you can indirectly protect grandparents, or co-workers without kids," Medlock said.

U.S. health advisers have targeted 160 million people to be first to get vaccinated against the new pandemic H1N1 flu starting in October. Each person will likely need two doses and only 45 million doses will be ready by then, so officials must prioritize.

CDC advisers last month recommended that pregnant women; people who care for babies; children and young adults aged 6 months to 24 years, people with chronic diseases such as asthma and healthcare workers be the first protected against the H1N1 virus, with others to follow as vaccine becomes available.

Their decision was based in part on who is at most risk of complications from H1N1 flu, which strikes younger people harder than seasonal flu does.

But Medlock's team said fighting spread may be better than protecting individuals.

"Flu vaccine is not 100 percent effective at blocking infection. If you can prevent people from being exposed to begin with, it is more effective than vaccinating people at risk," Medlock said in a telephone interview.

"The data is probably quite useful in Western Europe almost directly. As far as the developing world, my guess is the number of vaccines they will have will be severely limited."

In cases of severe shortages, he said it is likely better to target those most apt to become very ill.

AstraZeneca's MedImmune unit, CSL, Baxter GlaxoSmithKline Plc, Novartis AG and Sanofi-Aventis SA are among the companies making pandemic H1N1 vaccines.

(Editing by Maggie Fox and Cynthia Osterman)