Estimation of Grade-Specific, 2-Dose Varicella Vaccination Coverage In Minnesota Using School Immunization Record Data

Background:  Published reports of grade-specific varicella vaccination coverage rates are scarce. The ACIP first recommended one dose of varicella vaccine in 1995 and updated the recommendation to two doses in 2007. For entry into kindergarten and 7th grade, Minnesota began requiring one dose of varicella vaccine in 2004 and 2 doses in 2009. 

Objectives: Estimates of vaccine coverage for grades K-12 were obtained to determine possible temporal relationships in vaccination rates with the changes in school entry requirements for one and two doses of varicella vaccine.

Methods: During the 2009-2010 school year, school health personnel from 79 randomly selected schools were asked to report aggregate counts of students' documented varicella vaccine and disease history. The 74 schools returning data were also sent a follow-up survey regarding vaccination record update practices.

Results: Mean two-dose coverage rates were highest in kindergarten and seventh grade (86.5% and 81.1%, respectively). Mean two-dose coverage rates exceeded 50% among first (78.2%), second (55.6%), and eighth grades (53.5%). Mean two-dose coverage rates were lowest among students in eleventh grade (7.4%). Among elementary school students, 5^th-graders had the lowest two-dose coverage rates (10.7%) and highest one-dose-only coverage rate (83.7%). This cohort entered kindergarten in 2004, the year that the one-dose school entry law was implemented.  

Conclusions: Our results demonstrate that two-dose varicella vaccine coverage was highest in grades covered by the school immunization law; however, students in grades not currently covered by the school law also had higher than expected two-dose coverage rates. The chief limitation of our data is that school records are not updated every year for all students.