Varicella Vaccine Safety and Monitoring
Information for Healthcare Providers
Single-antigen Varicella Vaccine (Varivax®)
Since Varivax® was licensed, it has been very safe.
From March 1995 to December 2005, almost 48 million doses have been given to people in the United States. During that time, there were 25,306 adverse events reported to the Vaccine Adverse Event Reporting SystemExternal (VAERS). The most common events were rash, fever, or pain, redness, or soreness at the injection site.
In pre-licensure safety studies, 2 doses of Varivax have shown to be as safe as 1 dose of the vaccine.
Combination Measles, Mumps, Rubella, and Varicella Vaccine (ProQuad®)
In pre-licensure safety studies—
- more people had fever after the combination measles, mumps, rubella, and varicella (MMRV) vaccine than people who got MMR and varicella vaccines separately (22% compared to 15%)
- 3% of people got measles-like rash after MMRV compared with 2% of people who got the vaccines separately
The fever and rash usually occurred 5 to 12 days after MMRV or MMR and varicella vaccination and resolved quickly without long-term problems.
In a post-licensure cohort study, children who got MMRV for their first vaccinations at 12 through 23 months old had a greater risk of febrile seizure 5 to 12 days after their vaccination. This was in comparison to children who got MMR and varicella vaccines separately as their vaccinations (8 of out 10,000 vaccinations compared to 4 out of 10,000 vaccinations; adjusted relative risk of 2).
Studies showed that there were less adverse events after the second dose of MMRV than after the first dose. No serious adverse events were reported after 2 doses of MMRV vaccine. Post-licensure data do not suggest that children 4 through 6 years old who get MMRV as a second dose have an increased risk of febrile seizures in comparison to children who get separate MMR and varicella vaccines.
For more information, see Vaccine Safety: Measles, Mumps, Rubella, and Varicella (MMRV).
Rash and Herpes Zoster After Vaccination
Rash from varicella vaccine is usually mild. The risk of spreading varicella from this rash appears to be very low.
After a person is vaccinated, they can get infected with wild-type varicella-zoster virus (VZV). This is called breakthrough varicella. It is usually mild, but it is still contagious.
People who get a rash after their varicella vaccination should follow the same recommendations as unvaccinated people who get varicella. They should stay at home until their lesions have crusted over or no new lesions appear with 24 hours. Specimens from the rash may be sent to the National VZV Laboratory to determine whether the rash is due to vaccine-strain or wild-type VZV.
Since varicella vaccine contains a live virus, it can cause latent infection and subsequent reactivation. This can be similar to that caused by wild-type VZV. Consequently, there have been reported cases of herpes zoster in vaccinated people that were documented as being caused by vaccine-strain VZV. However, the risk of getting zoster from the vaccine-strain VZV is lower than the risk of getting zoster after infection with wild-type VZV.
Vaccine Safety Monitoring
VZV strain identification is needed to understanding adverse events from varicella vaccination. The CDC National VZV Laboratory provides VZV strain discrimination testing for laboratory confirmation of vaccine adverse events.
For more information, see Collecting Specimens for Varicella Zoster Virus (VZV) Testing and Interpreting Laboratory Tests. Download the VZV Specimen Collection Form.
All adverse events associated with varicella vaccine should be reported to the Vaccine Adverse Event Reporting System (VAERS) at 1-800-822-7967 or through the VAERS websiteExternal. This information is used to monitor vaccine safety.
- Chaves SS, Haber P, Walton K, Wise RP, Izurieta HS, Schmid DS, et al. Safety of varicella vaccine after licensure in the United States: experience from reports to the vaccine adverse event reporting system, 1995-2005External. J Infect Dis. 2008 Mar 1;197 Suppl 2:S170-7.
- Wise RP, Salive ME, Braun MM, Mootrey GT, Seward JF, Rider LG, et al. Postlicensure safety surveillance for varicella vaccineExternal. JAMA. 2000 Sep 13;284(10):1271-9.
- Prevention of Varicella—Recommendations of the Advisory Committee on Immunization Practices MMWR. 2007 June
- Use of Combination Measles, Mumps, Rubella, and Varicella Vaccine—Recommendations of the Advisory Committee on Immunization Practices MMWR. 2010 May