Uptake of Live Attenuated Influenza Vaccine Among Children in Selected Populations of the United States, 2008–2012

BACKGROUND: The Advisory Committee on Immunization Practices (ACIP) recommends annual influenza vaccination for all persons in the United States aged ≥6 months. ACIP currently indicates no preference between the trivalent influenza vaccine (TIV) or live attenuated influenza vaccine (LAIV) among persons eligible for both formulations. Consideration of potential recommendations for LAIV versus TIV requires assessment of safety, efficacy, and acceptability/uptake. We used population-based vaccination surveillance data to assess trends in the relative uptake of LAIV among children in the United States.

METHODS: Immunization information systems (IIS) are confidential, population-based systems that consolidate data from vaccine providers. IIS sentinel sites, consisting of substantial portions of seven states and one city, provided IIS-based immunization coverage. For each influenza season during 2008–12, children 2–18 years of age vaccinated with seasonal influenza vaccine were classified as having received TIV only or LAIV only. We used SAS^® 9.3 and Microsoft^® Excel^® 2010 to calculate unweighted intra-site means for Census-based coverage and proportions of vaccinated children who received either formulation during each influenza season. 

RESULTS: Seasonal influenza vaccinations were reported each influenza season during 2008–12 for approximately 935,000 children aged 2–18 years (range: 3,646–414,473 vaccinated children per site annually). During this period, influenza vaccination coverage with ≥1 dose increased from 17.3% to 26.7% among 2–18 year olds. During the 2008–09 season, 22.7% of vaccinated children received LAIV only, increasing to 36.5% during the 2011–12 season. During the 2011–12 season, relative uptake of LAIV among vaccinated children ranged from 19.1–51.1% between sites, and LAIV use was highest among 5–12 year olds (41.4% of vaccinated children), followed by 2–4 year olds (36.0%), and 13–18 year olds (24.9%).  

CONCLUSIONS: During the 2008–12 influenza seasons, LAIV has composed an increasing proportion of influenza vaccines administered to a selected population of children in the United States, with the exception of decreases in two sites during the 2011–12 season, which may correspond to government funding reductions for publicly purchased vaccines. Although IIS sentinel site data are not nationally representative, these provider-verified data enable timely assessments in selected populations. Choices between formulations might be influenced by factors including price, shelf life, patient preferences, and perceptions of safety and effectiveness. Patient age and eligibility for publicly purchased vaccines might also contribute to site-specific variability in LAIV uptake. These considerations should be investigated in order to optimize coverage and inform policy.