How many days you will have a reaction to the chickenpox vaccine varies from person to person, and it is usually possible to have a reaction up to a week after the shot. Some people may develop a fever within 1 to 3 days after receiving the varicella vaccine, which can be either high or low. In this case, drinking plenty of warm water and using fever-reducing medications, such as ibuprofen, as prescribed by the doctor, if necessary, can reduce the fever. Another part of the patient will have an allergic reaction, can be one day after the vaccine, can also be a few days later, can appear localized rash, itching and other manifestations, can use loratadine and other anti-allergic treatment. Chickenpox vaccine will also appear local injection site of redness, swelling, heat, pain, may last about 1 to 2 weeks, pay attention to protect the local skin, usually will slowly improve. Adverse reactions to varicella vaccine, it is recommended to go to the hospital, under the guidance of specialists to use medication, do not self-medication.