Will post-exposure use of the vaccine prevent or modify varicella?
Yes, the vaccine may prevent or modify illness when administered within 3 to 5 days after exposure. The ACIP now recommends vaccination of susceptible persons who are eligible for vaccination as soon as possible after exposure–ideally within 3 days but possibly up to 5 days of an exposure–to prevent illness or modify disease severity. If a person has already been infected, and the vaccine is given soon enough, disease may be modified or prevented. If the person was infected >5 days prior to vaccination, there is unlikely to be any benefit from vaccination but vaccination is not known to be harmful. Finally, exposure even in a household setting does not result in transmission 100% of the time. So, if the exposed person has not been infected, vaccination will confer protection against subsequent exposures. For further information, visit the following site: http://www.cdc.gov/epo/mmwr/preview/mmwrhtml/rr4806a1.
