The Impact of MMRV Vaccine Availability On the Coverage with MMR- and Varicella-Containing Vaccines Among Young Children, National Immunization Survey, 2005-2008

Background: The combination measles-mumps-rubella-varicella (MMRV) vaccine was licensed in the U.S. in September 2005.  Since July 2007, production of MMRV vaccine was suspended because of manufacturing constraints.  The impact of the availability of MMRV vaccine on coverage with measles-mumps-rubella (MMR)- and varicella-containing vaccines has not been reported.

Objectives: To estimate coverage with MMRV vaccine and MMR- and varicella-containing vaccines by birth cohorts, and evaluate trends in MMR- and varicella-containing vaccines coverage before, during and after the period of MMRV vaccine availability.

Methods: Coverage was estimated by monthly birth cohort, using National Immunization Survey 2005-2008 data for at least one dose of MMR vaccine, one dose of varicella vaccine and one dose of MMRV vaccine for children by 19 months of age. Cohorts born from May 2003 through March 2007 were included in the study; this period covered children who were 12-19 months old during the time of MMRV availability. To assess MMR-containing vaccine coverage, doses of MMR and MMRV vaccines were combined; to assess varicella-containing vaccine coverage, doses of varicella and MMRV vaccines were combined. Coverage trends were assessed using polynomial regression. Data analyses were performed with SUDAAN software.

Results: During the study period, the MMR- and varicella-containing vaccines coverage remained constant (p-values = 0.76 and 0.23 for test of linear trend). For children born after June 2004, MMRV coverage increased dramatically from 1% to a peak of 47% for children born in January 2006 (p-value<0.001), then significantly dropped to 2% for those born in March 2007 (p-value<0.001). Birth cohorts born between December 2005 and April 2006 had received 40%-47% of their MMR- and varicella containing vaccines as MMRV vaccine.

Conclusions:MMR- and varicella-containing vaccines coverage by 19 months of age does not appear to have been affected by the introduction and suspension of MMRV vaccine.