Background: The Advisory Committee on Immunization Practices recommends that influenza vaccine naïve children aged <9 years receive two doses in the current season to be fully vaccinated. Previously vaccinated children aged <9 years are recommended to receive two doses in the current season if they received only one dose for the first time in the previous season, and are recommended to receive only one dose in all other cases.
Objectives: Assess the impact of vaccination history on completion of the two-dose influenza vaccine series among children aged 6-59 months during the 2007-08 season.
Methods: Data from the eight IIS sentinel sites were used to calculate the percentage of children aged 6-23 months (n=302,333) and 24-59 months (n=808,711) recommended to receive one or two doses to be fully vaccinated in 2007-08 season and the percentage who completed the recommended doses. The association between influenza vaccination history and vaccination status in the 2007-08 season was assessed.
Results: Ninety-three percent of children aged 6-23 months were recommended to receive two influenza vaccine doses in the 2007-08 season; 16.8% of this subset of children completed both doses. Two-thirds (65.6%) of children aged 24-59 months were recommended to receive two doses; 1.7% of this subset of children received two doses. Among children aged 24-59 months who were recommended to receive two doses in the 2007-08 influenza season, those who received two doses were significantly more likely to be vaccine naïve at the beginning of the season than to have been primed in the previous season (OR=2.6, 95% CI=2.4-2.7).
Conclusions: Although most children aged 24-59 months were recommended to receive two influenza vaccine doses to be fully vaccinated, very few received both doses. Barriers to completing the 2-dose series, particularly among children aged 24-59 months need to be identified so that effective interventions can be implemented.