Giving flu vaccines to children can help protect the wider community, a new study shows.

The findings, published this week in the Journal of the American Medical Association, support the concept of "herd immunity," in which vaccinated members of a community provide a barrier against a disease for those who are unvaccinated.

Researchers, including the study's lead author, Dr. Mark Loeb, of McMaster University in Hamilton, Ontario, say the trial was conducted in 46 Hutterite colonies of a self-confined religious community in Canada. The Hutterites are an Anabaptist group similar to the Amish who live mostly in rural areas in western Canada and have little contact with non-Hutterite people around them.

During the 2008-09 flu season, researchers administered vaccines to 947 children between the ages of 3 and 15. Of those, 502 children in 22 colonies got the seasonal flu vaccine and the 445 children in the other 24 colonies were given the hepatitis A vaccine, the study says. There were more than 2,000 unvaccinated people in the combined communities.

Six months after children were given the vaccines, 119 unvaccinated community members were confirmed by a laboratory as having contracted the flu. Of those, far fewer were from the colonies where children had been given the flu shot -- 39, as opposed to 80 from the colonies where children had been given the hepatitis A vaccine, according to the JAMA report.

The vaccine was 61 percent effective at indirectly warding off the disease, the researchers concluded, and the findings "offer experimental proof to support selective influenza immunization of school-aged children," they state.

Because children and adolescents appear to play a key role in spreading the flu, selectively vaccinating them may interrupt transmission, the study's authors write.

Learn more about how herd immunity works here.

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