Vaccine Info

Varivax Varicella Vaccine

Last Reviewed
January 26, 2021

Varivax Varicella Vaccine Description

Varivax is a live, attenuated varicella-zoster vaccine, a weakened form of the chickenpox virus.

Varivax is a preparation of the Oka/Merck strain of live, attenuated varicella virus. The virus was initially obtained from a child with wild-type varicella, then introduced into human embryonic lung cell cultures, adapted to and propagated in embryonic guinea pig cell cultures, and finally propagated in human diploid cell cultures (WI-38).

Further passage of the virus for varicella vaccine was performed at Merck Research Laboratories (MRL) in human diploid cell cultures (MRC-5) that were free of adventitious agents.

This live, attenuated varicella vaccine is a lyophilized preparation containing sucrose, phosphate, glutamate, and processed gelatin as stabilizers.

Varivax Varicella Vaccine Indication

It is a vaccine indicated for active immunization for the prevention of varicella (ChickenPox) in individuals 12 months of age or older.

Varivax Varicella Vaccine Dosage

Varivax is administered by subcutaneous injection.   

The duration of protection of Varivax is unknown; however, long-term efficacy studies have demonstrated continued protection up to 10 years after vaccination.

A boost in antibody levels has been observed in vaccinees following exposure to wild-type varicella which could account for the apparent long-term protection after vaccination in these studies.

According to the CDC, due to the nature of Varivax, a weakened live vaccine, it is possible for the recipient of this vaccine to develop shingles later in life.

Varivax Varicella Vaccine News

October 29, 2020 - Varicella-Zoster Virus and Human Papillomavirus Vaccination in Immunocompromised Patients. The presence of immunocompromise requires special attention to several aspects of vaccination. The first is safety: Live attenuated vaccines are “weakened” but potentially have viable virus. This may cause disseminated infection in severely immunocompromised patients, and live vaccines are therefore generally avoided. Inactivated vaccines do not contain live virus and cannot cause disseminated infection; therefore, they are safer. 

August 27, 2019 - Varicella rates drop after vaccine introduced; same expected with zoster. A live attenuated varicella vaccine (Oka strain) was developed in the 1970s in Japan. The vaccine (Varivax) was licensed for use as a single dose in the United States in 1995, and the United States became the first country to introduce a universal varicella vaccination program.

Varivax Varicella Vaccine Clinical Trials

Merck's Varivax has been in over 110 clinical trials.