Varicella immunogenicity with 1- and 2-dose regimens of measles-mumps-rubella-varicella vaccine.

A quadrivalent vaccine combining measles, mumps, rubella, and varicella antigens (MMRV) was developed to increase the coverage of varicella vaccine and reduce the number of injections children receive. Although the varicella antigen is as immunogenic in the latest formulation of MMRV vaccine as when it is administered alone, up to 14% of vaccine recipients do not achieve protective levels of anti-varicella antibodies after a single dose, which can result in breakthrough varicella. A second dose of varicella vaccine raises response rates to 99% and was recently recommended by the Advisory Committee on Immunization Practices. Giving the second dose 3 months after the first (at approximately 15 months of age) would provide more protection against varicella but would necessitate a change in the childhood vaccination schedule, which currently calls for a second dose of MMRV vaccine between the ages of 4 and 6 years.