Background: Strategies to improve vaccine series completion include minimizing the required number of doses. Three-dose RotaTeq (RV5) is administered at ages 2, 4, and 6 months; and 2-dose Rotarix (RV1) is administered at ages 2 and 4 months.
Objectives: To determine whether a shorter dosing series improves rotavirus vaccine series completion and dose compliance.
Methods: Infants aged less than 1 year who initiated a rotavirus vaccine from 01 January 2009 to 30 June 2009 and were continuously enrolled through age 9 months were identified using US health insurance claims data. Infants were observed until the earliest of: disenrollment from the health plan, age 1 year, or 31 Mar 2010. Three cohorts were formed based on receipt of the same brand (RV1 or RV5) for all doses or receipt of a mixed series. Valid doses (i.e., doses administered after age 6 weeks and at least 4 weeks following the previous dose) were required for series completion. Age at series completion was calculated. Adherence is reported as the percentage of valid doses aligned with the Advisory Committee on Immunization Practices rotavirus vaccine schedule.
Results: A greater proportion of infants in the RV1 cohort (N=6130) than in the RV5 cohort (N=49,454) completed their respective series (91.0% vs. 83.4%; P<0.001). A valid 3-dose series was completed by 67.5% of the mixed cohort (N=2616). Series completion occurred at a younger age (mean±SD) for infants receiving RV1 (130.2±17.1 days) versus RV5 (191.3±14.5 days; P<0.001). Schedule adherence ranged from 93.6% to 99.8% across doses and cohorts.
Conclusions: Most infants who initiated a rotavirus vaccine completed the required series, but the proportion was higher and completion earlier for children whose full series required 2 doses rather than 3.