If this is her first vaccination for varicella or chickenpox there is a small chance (about 13%) of break through disease.  That means a sampling of children break out with a rash, low fever, and manifest chickenpox about 10 days to three weeks after vaccination.  If this is her booster, it is unlikely she will have any reaction except tenderness at the injection site for a short time.  However, no one can predict an individual's reaction. Allergic response sometimes happens.  There are no precautions to take other than not being pregnant and ill at the time of immunization.  The CDC and the American Academy of Pediatrics have hand outs given to patients when receiving immunizations. Read them before and ask your physician any questions you have. Check out our special edition on the home page about immunizations. Thanks and a great question.
 
Wayne A. Yankus, MD, FAAP
expert panelist: pediatrics