Background: A combined measles, mumps, rubella and varicella (MMRV) vaccine would facilitate universal immunization against 4 diseases by decreasing the number of injections and thus enhancing compliance and coverage rates. If a second dose of varicella vaccine were to be recommended, MMRV could be used to administer a routine second dose of M-M-R®II with the added advantage of boosting varicella-zoster virus (VZV) antibody titers.
Methods: Subjects 12–23 months of age received a single injection of 1 of 3 lots of an MMRV vaccine (ProQuad) containing high, middle or low VZV potency, or VARIVAX given concomitantly with M-M-R®II. Recipients of MMRV received a second injection of MMRV ∼90 days later.
Results: We enrolled 1559 subjects in the study. Antibody response rates to VZV 6 weeks after 1 injection of high potency MMRV (88.6%) or 2 injections of MMRV of any varicella potency (99.7–100%) were similar to the response rates after concomitant administration of M-M-R®II and VARIVAX (93.1%). The second injection of MMRV boosted VZV antibody titers. Antibody responses to measles, mumps and rubella were ≥98%, similar to the control, after 1 or 2 injections of MMRV. MMRV was generally well-tolerated during the 42 days after vaccination.
Conclusions: One injection of high potency MMRV resulted in antibody responses to the 4 vaccine components equivalent to those found after concomitant administration of M-M-R®II and VARIVAX. A second injection of MMRV resulted in a significant boost in VZV antibody. This boost may translate into enhanced immunogenicity against varicella, which is known to correlate with increased protection.