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Vaccinating Children to Produce "Community Immunity"

Can vaccinating a large percentage of its children protect a community from a possible flu epidemic?

Photo of Pedro Piedra, M.D.
Pedro Piedra, M.D.
That's a key question researchers from Baylor College of Medicine, Houston, are trying to answer through a large-scale vaccination effort in the towns of Temple and Belton, Texas (population 65,000-70,000). The NIAID-supported study is a continuation of an earlier clinical study. That study found that immunizing 20 to 25 percent of children in the two communities over a four-year period indirectly helped protect 8 to 18 percent of adults in the area from the flu.

This indirect effect, called herd or community immunity, results when a sufficient portion of a community has been immunized, so that even those who haven't been vaccinated escape infection because fewer people can transmit the virus. Children are often a source of the flu virus, passing it onto their friends, teachers, and families.

In the earlier study, researchers also found that the nasal spray flu vaccine in children 18 months to 18 years of age, the primary vaccination method, was safe and offered significant protection from the flu, with one dose frequently lasting through at least two flu seasons. Available commercially as FluMist, for healthy people ages 5 to 49 years, the nasal spray flu vaccine protects against three flu strains.

In the follow-up study, principal investigator Pedro Piedra, M.D., and his colleagues are expanding their reach. They will be attempting to double the number of children they vaccinate by developing a widespread school-based vaccination program. In doing so, they are hoping to prevent the spread of influenza among the younger population as well as adults. (In the follow-up study, only healthy children ages 5 to 18 can receive FluMist, due to Food and Drug Administration guidelines. Other age-eligible children will be offered a regular flu shot.)

The researchers also are hoping to answer the $100 million question: how many children need to be vaccinated to get 100 percent protection in a community?

Assisting in the study are healthcare professionals from Scott and White Clinic and Hospital, Houston.

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Last Updated August 13, 2010