Varivax is not the same thing as varicella, but the two terms are closely related. Varicella is the medical name for chickenpox, the disease caused by the varicella-zoster virus. Varivax is the brand name for the vaccine that prevents it. Think of it like the difference between “flu” and “Fluzone”: one is the illness, the other is a specific product designed to protect you from it.
How Varivax and Varicella Are Related
The FDA lists Varivax’s proper name as “Varicella Virus Vaccine Live,” which is where the confusion often starts. On medical records, immunization forms, and pharmacy labels, you might see “varicella vaccine,” “Varivax,” or both used interchangeably. They refer to the same shot. Varivax is manufactured by Merck and is approved for anyone 12 months of age and older.
The vaccine contains a weakened (live attenuated) form of the varicella-zoster virus called the Oka/Merck strain. Because the virus is alive but weakened, it triggers your immune system to build defenses without causing a full-blown case of chickenpox. The vaccine contains no preservatives.
What About ProQuad (MMRV)?
There’s also a combination vaccine called ProQuad, sometimes referred to as MMRV, that bundles protection against measles, mumps, rubella, and varicella into a single shot. It contains the same varicella component as Varivax but adds three other vaccines. Some children receive ProQuad instead of getting separate MMR and Varivax injections. One thing to be aware of: the risk of fever-related seizures is slightly higher with MMRV compared to giving the shots separately, particularly with the first dose in younger children.
How Well Varivax Works
A single dose of the varicella vaccine is about 82% effective at preventing any form of chickenpox and nearly 100% effective at preventing severe cases. Two doses raise protection significantly. In the clinical trial conducted before the vaccine was licensed, two doses were 98% effective against any chickenpox and 100% effective against severe disease. Real-world studies after the vaccine became widely available found two-dose effectiveness around 92%, with a range of 88% to 98%.
In practical terms, a fully vaccinated person who does catch chickenpox typically gets a very mild case, often with fewer than 50 skin lesions and little to no fever, compared to the hundreds of blisters and high fevers that unvaccinated children commonly experience.
Recommended Dosing Schedule
For children, the CDC recommends two doses: the first between 12 and 15 months old, and the second between ages 4 and 6. Adolescents and adults aged 13 and older who were never vaccinated and have no evidence of prior immunity should receive two doses spaced 4 to 8 weeks apart. If more than 8 weeks pass between doses, you don’t need to start over. The second dose can simply be given whenever you get to it.
Common Side Effects
The varicella vaccine is well tolerated overall. The most frequently reported reactions are injection site soreness or redness (about 31% of recipients), a mild rash (28%), and fever (12%). The rash sometimes looks like a few small chickenpox-like bumps near the injection site or scattered on the body. It typically appears within a few weeks of vaccination and resolves on its own. Itching or hives occur in roughly 9% of cases.
Who Should Not Get the Vaccine
Because Varivax contains a live virus, it’s not appropriate for everyone. The vaccine is contraindicated during pregnancy. People with significantly weakened immune systems, whether from medical conditions or medications that suppress immunity, should also avoid it. If someone in these groups is exposed to chickenpox, a different product called varicella-zoster immune globulin can be given to help prevent or reduce the severity of infection.
If you’re looking at an immunization record and trying to figure out whether “varicella” and “Varivax” are the same entry, they almost certainly are. One is simply the clinical term for the disease, and the other is the product name printed on the vial.