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Varicella Vaccine May Be Helpful After Exposure to Chickenpox

Varicella is the virus that causes chickenpox. Most cases of chickenpox are resolved in a week’s time. However some cases can cause serious complications. Other infection may develop and the varicella virus can cause shingles later in life. Pregnant women and developing fetuses are also at higher risks for serious complications. The varicella vaccine given before exposure can decrease the chance of infection and decrease the severity of the illness if an infection does occur.

While vaccines are designed to be given before exposure, the Cochrane Library reviewed the benefit of getting the vaccine after a recent exposure. The review found that the vaccine may help reduce the risk of contracting chickenpox or decrease the severity of the disease in people that were exposed and previously unvaccinated.

About the Study

The systematic review assessed three trials with a total of 110 children. The children were healthy and had household contact with someone infected with varicella. Most of the children received the vaccine within three days of exposure but the trials did vary. On comparing exposed children that received the vaccine versus those that did not:

  • Varicella developed in 23% of vaccinated vs. 78% of unvaccinated
  • Moderate to severe varicella developed in 2% of vaccinated vs. 76% of unvaccinated
  • Most vaccinated participants that developed varicella had mild disease, less than 50 lesions

Some of the studies had design flaws. One of the studies was of higher quality and found that the rate of the development of varicella was not significantly different between the two groups. However, it did find that the incidence of moderate to severe cases were reduced in the vaccinated group (4.5%) compared to the unvaccinated group (40%).

How Does This Affect You?

While there was a difference between the studies in the ability of the vaccine to prevent the infection after exposure, the review did suggest that the vaccine was effective in reducing the severity of the illness. The vaccination is best used before exposure but may be used as a preventative tool for unvaccinated household members that are exposed to varicella.

Talk to you doctor about a vaccine schedule for your child. If you have never been exposed to chickenpox nor received a vaccination, talk to your doctor about your options.




Last reviewed November 2008 by Larissa J. Lucas, MD

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