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The MMRV vaccine combines the attenuated virus MMR (measles, mumps, rubella) vaccine with the addition of chickenpox vaccine or varicella vaccine (V stands for varicella). The MMRV vaccine is typically given to children between 1 and 2 years of age.
Several companies supply MMRV vaccines. ProQuad is marketed by pharmaceutical giant Merck and was approved in 2005 for use in the United States by the Food and Drug Administration for children ages twelve months through twelve years. A live attenuated virus MMRV vaccine called Priorix Tetra  by GlaxoSmithKline has been approved in Germany and Australia.
The World Health Organization recommends vaccinating against measles, mumps, rubella (German measles), and varicella (chickenpox) because the risks of these diseases far outweigh the risks of vaccinating against them. In particular, the World Health Organization recommends varicella vaccination in countries where the vaccine is affordable, the disease is a relatively important problem, and high and sustained coverage can be achieved. The U.S. and a few other countries have widely implemented this. MMR and varicella vaccine are given at roughly the same time and a booster injection is recommended for both. The MMRV vaccine, a combined MMR and varicella vaccine, simplifies administration of the vaccines.
In May, 2007, the manufacturer Merck announced that, due to manufacturing problems in the chickenpox component, the Merck vaccine ProQuad is not available. In August 2007, Merck announced that they did not know whether ProQuad would be made available in 2008 due to an issue with its bulk manufacturing process, but their goal was to restore its availability as soon as possible.
- For individuals who are moderately or severely ill, it is generally recommended that they wait until after recovery before getting ProQuad. No such precautions are recommended for minor illnesses, such as a cold.
- It is recommended that aspirin or aspirin containing products be avoided for at least six weeks after receiving ProQuad vaccine (Aspirin is not recommended in children under 14 in any case). A serious condition called Reye's Syndrome has been reported in patients with chicken pox.
- Individuals should not receive ProQuad without first consulting their doctor if there is a history of a life-threatening allergic reaction to gelatin, eggs, the antibiotic neomycin, or a previous MMR or chicken pox vaccine.
Doctors are advised to be aware of whether or not a patient has HIV, AIDS or another disease that affects the immune system, is taking a medication that affects the immune system, has cancer, a fever or active untreated tuberculosis, is receiving cancer treatment, or has ever had a low platelet count (a blood disorder).
Adverse events 
Rare but serious adverse events reported following ProQuad vaccination include allergic reactions, including swelling of the lips, tongue, or face; difficulty breathing or closing of the throat; hives; paleness; weakness; dizziness; a fast heart beat; deafness; long-term seizures, coma, or lowered consciousness; permanent brain damage; seizures (jerking or staring) caused by fever; or temporary low platelet count.
For children age two and younger, the MMRV vaccine is associated with more adverse events compared to separate administration of MMR and varicella vaccinations on the same day. There are 4.3 additional febrile seizures per 10,000 vaccinated children (95% CI 2.6-5.6), 7.5 additional mostly mild fever episodes per 100 vaccinated children (95% CI, 5.4-9.4) and 1.1 additional measles-like rash per 100 children (95% CI, 0.2-1.8). Febrile seizures cased by the MMRV vaccine occur 7 to 10 days after vaccination. In children age 4-6, there is no evidence for an increased risk in febrile seizures after MMRV compared to the separate administration of MMR and Varicella vaccines.  .
- GSK: Priorix Tetra Studies
- GlaxoSmithKline PLC (GSK) Full Description | Stocks | Reuters.com
- Vesikari T, Sadzot-Delvaux C, Rentier B, Gershon A (2007). "Increasing coverage and efficiency of measles, mumps, and rubella vaccine and introducing universal varicella vaccination in Europe: a role for the combined vaccine". Pediatr Infect Dis J 26 (7): 632–8. doi:10.1097/INF.0b013e3180616c8f. PMID 17596807.
- Netzer TM (2007-08-28). "Dear valued customer" (PDF). Retrieved 2007-09-19.
- CDC: Possible Side-effects from Vaccines
- Klein NP, Fireman B, Yih WK, et al. (July 2010). "Measles-mumps-rubella-varicella combination vaccine and the risk of febrile seizures". Pediatrics 126 (1): e1–8. doi:10.1542/peds.2010-0665. PMID 20587679.
- FDA: CBER clinical review of studies submitted in support of licensure of ProQuad
- CDC.gov Licensure of a Combined Live Attenuated Measles, Mumps, Rubella, and Varicella Vaccine (Merck ProQuad)
- FDA.gov - Product Approval Information - Licensing Action: Measles, Mumps, Rubella and Varicella Virus Vaccine Live (ProQuad) Merck & Co', Food and Drug Administration (September 6, 2005)
- MedicalNewsToday.com - 'Cochrane Library publishes the most thorough survey of MMR vaccination data', Medical News Today