Varivax is a live, attenuated vaccine derived from varicella virus and indicated for prophylaxis against varicella disease in humans aged 1 year and older. Known as chickenpox in children and adolescents and as shingles in adults and populations, this disease caused by varicella-zoster virus is highly contagious and exhibits a peak incidence of occurrence in children aged 5-9 years. Varicella is a self-limiting disease mostly accompanied by fever 100 F+ (orally) and the expression of numerous (300-500) maculopapular and/or vesicular lesions. Varicella disease is rarely more than a short-lived, uncomfortable condition, but has been associated with more serious and even fatal events such as bacterial superinfection, Reye's Syndrome, pneumonia and encephalitis.
Varivax is packaged as a lyophilized preparation containing no preservatives and must be stored frozen (-15 C/+5 F) until reconstituted. Reconstituted preparations are sterile, should be used immediately and should be discarded after 30 minutes post reconstitution. Varivax should not be frozen after reconstitution.
Varivax is administered subcutaneously and should never be injected intravenously. Children aged 1 to 12 years should receive a single 0.5 ml dose. Adults older than 13 years should receive a 0.5 ml dose followed by a second 0.5 ml booster dose 4 to 8 weeks later.
The duration of protection of Varivax is not known at present, and it is thought that some individuals in a highly immunized population may experience decreased immune protection against varicella due to decreased exposure to the natural virus. Furthermore, vaccination with Varivax does not guarantee immune protection for all individuals, though early clinical trials showed an average decreased incidence of varicella disease of 67% in children aged 1-9 years with 2.1% - 3.6% of vaccines reporting chickenpox versus 8.3% - 9.1% incidence expected in the non-vaccinated population.
Contraindications to use of Varivax include hypersensitivity to any of the vaccine components and use in individuals with immunodeficiency states. Varivax is not contraindicated in those individuals with chicken/egg allergies and can be administered concurrently with M-M-R II vaccine. Vaccine recipients should be cautioned to avoid use of salicylates for 6 weeks post-vaccination as Reye's Syndrome has been reported following the use of salicylates during natural varicella infection.