Two Dose Varicella Vaccination Coverage Estimates From Immunization Information System (IIS) Sentinel Sites, 2010

Background:  In 2006, the Advisory Committee on Immunization Practices (ACIP) recommended a routine two-dose varicella vaccination program for children, with the first dose administered at 12-15 months and the second at 4-6 years. One-dose varicella vaccination coverage is currently estimated using the National Immunization Survey for children aged 19-35 months but no population-based data are available to assess two-dose varicella vaccination coverage.

Objectives:  To estimate two-dose varicella vaccination coverage in children 4-6 years of age, assess the age at first and second dose, and determine frequency of co-administration with MMR vaccine.

Methods:  Data from January 2006 to June 2010 were collected to estimate one- and two-dose varicella and MMR vaccination coverage among children from eight Immunization Information System (IIS) sites. Analyses were limited to children aged 4-6 years.

Results: An average of 66.7% of children aged 4-6 years had received their first dose of varicella vaccine by 15 months of age; 31.1% and 46.3% received their second dose at 4 and 5 years, respectively. The unweighted average two-dose varicella vaccination coverage among children aged 4-6 years was 56.4% (range, 32% to 67%) compared to two-dose MMR coverage of 71.2%. Among the 77.5% of children who received at least 1 dose of varicella and MMR-containing vaccines, 65.5% received the vaccines separately but during the same visit and 31.4% received both but at different visits; 3.1% received MMRV. For the second dose, 41.7% received the vaccines separately but simultaneously and 36.1% received them both on different visits; 22.2% received MMRV.  

Conclusions: In the first three years of the two-dose varicella vaccination program, over half of 4-6 year olds have received two doses of varicella vaccine, however coverage lags behind that for MMR vaccine. Adoption of school entry requirements for a second dose of varicella vaccine is likely to increase two-dose varicella vaccination coverage levels further.