Chicken pox vaccine for children protects babies too, study shows

Vaccinating children who are more than a year old against varicella, or chicken pox, also provides “tremendous indirect benefits” to young babies, researchers reported Monday in the journal Pediatrics.

The U.S. implemented a variella vaccine program in 1995, offering the vaccine to children 12 months and older. But younger babies who aren’t old enough to get the vaccine are protected through so-called “herd immunity” -- because fewer older kids develop chicken pox, the younger children are less likely to be exposed to the virus.

The researchers -- representing a variety of agencies, including the Centers for Disease Control and Prevention -- studied data on chicken pox cases in the Antelope Valley near Los Angeles and in Philadelphia during the first 14 years the vaccine was available. Herd immunity had a powerful effect: The team found that the incidence of chicken pox in infants up to 11 months old fell nearly 90% between 1995 and 2008 -- and that decline was correlated with an increase in varicella vaccination coverage in both locations.

“This benefit reinforces the importance of maintaining high rates of varicella vaccination in the community to protect individuals who cannot be vaccinated because of age or medical contraindications,” the researchers wrote.

This latest piece of evidence in favor of vaccinating kids against varicella comes at a time when “pox parties” -- gatherings where parents expose their uninfected kids to children with chicken pox, with the idea that the uninfected kids will get varicella and, as a result, acquire immunity -- have been in the news. Some advocate the parties as a safe way to expose kids to chicken pox “naturally.” But doctors warn that chicken pox can cause serious complications and that the vaccine is safer.

Pediatrics has published the report on varicella in infants on the Web.

The CDC’s page on varicalla vaccinations explains more about the disease.

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