'Herd immunity' can help prevent spread of flu: study

Immunizing children against seasonal influenza can help block the spread of infection among nonvaccinated community members, finds a new study released this week from McMaster University in Hamilton, Ontario.

Researchers conducted a trial in 46 Hutterite religious colonies in Canada where residents have limited contact outside their own community. In 22 colonies, influenza vaccines were given to 502 children between 36 months and 15 years of age, or about 83 percent of the colonies' children. In the remaining colonies, children received a Hepatitis A vaccine as a control, the report said.

Researchers found that living in a community where at least 80 percent of children had received the flu vaccine was 61 percent effective at preventing the illness in nonvaccinated individuals. The concept is commonly referred to as "herd immunity."

The study was published in the March 10 issue of the Journal of the American Medical Association.