Safety and Immunogenicity of Human Serum Albumin-Free MMR Vaccine in US Children Aged 12-15 Months

Background. M-M-(RII)-I-TM (MMRII; Merck & Co) is currently the only measles-mumps-rubella (MMR) vaccine licensed in the United States. Another licensed vaccine would reinforce MMR supply. This study assessed the immunogenicity of a candidate vaccine (Priorix(TM), GlaxoSmithKline Vaccines [ MMR-RIT]) when used as a first dose among eligible children in the United States. Methods. In this exploratory Phase-2, multicenter, observer-blind study, 1220 healthy subjects aged 12-15 months were randomized (3: 3: 3: 3) and received 1 dose of 1 of 3 MMR-RIT lots with differing mumps virus titers (MMR-RIT-1 [4.8 log(10)]; MMR-RIT-2 [4.1 log(10)]; MMR-RIT-3 [3.7 log(10)] CCID50) or MMRII co-administered with hepatitis A vaccine (HAV), varicella vaccine (VAR) and 7-valent pneumococcal conjugate vaccine (PCV7). Immune response to measles, mumps, and rubella viruses was evaluated at Day 42 post-vaccination. Incidence of solicited injection site, general, and serious adverse events was assessed. Results. Seroresponse rates for MMR vaccine viral components in MMR-RIT lots were 98.3-99.2% (measles), 89.7-90.7%(mumps), and 97.5-98.8%(rubella), and for MMRII were 99.6%, 91.1%, and 100%, respectively. Immune responses to HAV, VAR, and PCV7 were similar when co-administered with any of the 3 MMR-RIT lots orMMRII. There were no apparent differences in solicited or serious adverse events among the 4 groups. Conclusions. Immune responses were above threshold levels for projected protection against the 3 viruses from MMR-RIT lots with differing mumps virus titers. MMR-RIT had an acceptable safety profile when co-administered with HAV, VAR, and PCV7.