On September 6, 2005, the Food and Drug Administration licensed a combined live attenuated measles, mumps, rubella, and varicella (MMRV) vaccine (ProQuad®, Merck & Co., Inc., Whitehouse Station, New Jersey) for use in children aged 12 months--12 years. The attenuated measles, mumps, and rubella vaccine viruses in ProQuad are identical and of equal titer to those in the measles, mumps, and rubella (MMR) vaccine, MMRII® (Merck). The titer of Oka/Merck varicella-zoster virus is higher in MMRV vaccine than in single antigen varicella vaccine, VARIVAX® (Merck), a minimum of 3.13 log10 plaque-forming units (pfu) versus 1,350 pfu (approximately 1.13 log10), respectively.
Advisory Committee on Immunization Practices (ACIP) current recommendations are that children aged 12 months--12 years receive 2 doses of MMR vaccine at least 1 month apart and 1 dose of varicella vaccine (1).* MMRV vaccine can decrease the number of injections received by children when all of the component antigens are indicated for administration. One dose of MMRV vaccine should be administered on or after the first birthday, preferably as soon as the child becomes eligible for vaccination (2).