The MMRV vaccine is a combination shot that protects against four viral diseases in a single injection: measles, mumps, rubella, and varicella (chickenpox). It’s given to children between 12 months and 12 years of age, combining what would otherwise require two separate shots into one. The only MMRV vaccine available in the United States is ProQuad, manufactured by Merck.
The Four Diseases It Prevents
Each letter in “MMRV” stands for one of the viruses targeted by the vaccine. All four are highly contagious and were once extremely common childhood illnesses.
- Measles causes fever, cough, runny nose, red and watery eyes, and a full-body rash. It can lead to serious complications including pneumonia and brain swelling.
- Mumps causes fever, headache, muscle aches, fatigue, and painful swelling of the salivary glands under the ears.
- Rubella causes fever, sore throat, rash, and eye irritation. It’s typically mild in children but extremely dangerous during pregnancy, where it can cause severe birth defects.
- Varicella (chickenpox) causes an itchy, blistering rash along with fever, tiredness, and loss of appetite. In rare cases it leads to skin infections, pneumonia, or brain inflammation.
How Well It Works
After one dose, the vaccine is 93% effective against measles, 72% effective against mumps, and 97% effective against rubella. A second dose pushes measles protection to 97% and mumps protection to 86%. Mumps is the hardest of the four to fully prevent, which is why outbreaks still occasionally occur even in vaccinated populations, but two doses provide strong protection against serious illness.
When Children Get It
The MMRV vaccine follows the same schedule as the separate MMR and chickenpox vaccines. The first dose is recommended between 12 and 15 months of age. The second dose is given between ages 4 and 6, typically before a child starts kindergarten. The vaccine is only approved for children 12 months through 12 years old.
MMRV vs. Two Separate Shots
The MMRV vaccine combines the MMR vaccine and the varicella vaccine into a single injection. The alternative is giving both shots separately at the same visit, which means two needle sticks instead of one. Both approaches provide the same protection, but there’s an important difference in side effects for younger children.
For the first dose in children 12 to 47 months old, the combination MMRV vaccine causes more fevers: about 22 out of every 100 children develop a fever of 102°F or higher, compared to about 15 out of 100 who get the two shots separately. More significantly, febrile seizures (brief seizures triggered by a rapid rise in body temperature) occur in roughly 8 out of every 10,000 children who get MMRV, compared to 4 out of 10,000 with separate shots. These seizures, while frightening to witness, are not harmful and don’t cause lasting problems.
Because of this difference, the CDC recommends that for the first dose in children under 4 years old, providers give the MMR and varicella vaccines as two separate injections, unless a parent specifically prefers the combination shot. For the second dose at any age, or for first doses given at age 4 and older, the combination MMRV is generally preferred since the seizure risk is no longer elevated in older children, and the second dose is less likely to cause fever than the first.
Common Side Effects
The most frequent reactions are mild: soreness where the shot was given, fever, a mild rash, and swollen glands in the cheeks or neck. These typically appear 5 to 12 days after vaccination and resolve on their own. Some children develop a faint chickenpox-like rash with just a few spots, which is a sign the immune system is responding to the vaccine.
Joint pain or stiffness can occur in up to 1 in 4 females past puberty who weren’t previously immune to rubella, usually starting one to three weeks after vaccination and lasting about two days. This is more relevant for older children and teens receiving a catch-up dose than for toddlers getting their routine shots.
A temporary drop in platelets (the blood cells that help with clotting) occurs in roughly 1 in 40,000 vaccinated children. This condition usually resolves without treatment within a few weeks.
Who Should Not Get the MMRV Vaccine
Children with severely weakened immune systems should not receive MMRV. This includes children undergoing chemotherapy, those with inherited immune disorders, or those on long-term medications that suppress immune function. Because the vaccine contains live but weakened viruses, it could cause illness in someone whose immune system can’t keep the weakened virus in check.
Other reasons to avoid or delay the vaccine include a previous severe allergic reaction to any component of the shot, a personal or family history of seizures (in which case separate MMR and varicella vaccines are recommended instead), recent receipt of a blood transfusion or other blood product (which can interfere with the immune response for up to 11 months), and moderate to severe acute illness at the time of the scheduled dose. Children taking antiviral medications used to treat herpes or chickenpox need to stop those drugs at least 24 hours before vaccination and avoid them for 14 days afterward, since the drugs could prevent the weakened vaccine virus from working properly.