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Antimicrob. Agents Chemother. doi:10.1128/AAC.00517-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Comparative Immunogenicity of Frozen and Refrigerated Formulations of Live Attenuated Influenza Vaccine in Healthy Subjects

Kentucky Pediatric Research, Bardstown, KY; Primary Physicians Research, Pittsburgh, PA; MedImmune, Gaithersburg, MD

^* To whom correspondence should be addressed. Email: slblock{at}pol.net.

	Abstract

The frozen version of live attenuated influenza vaccine (LAIV, FluMist®) was compared with a newly licensed, refrigerated formulation (CAIV-T) for immunogenicity, safety, and tolerability in healthy subjects 5–49 years of age. Eligible subjects were randomized 1:1 to receive CAIV-T or frozen LAIV. Subjects 5–8 years of age received 2 doses of vaccine, 46–60 days apart; subjects 9–49 years of age received 1 dose of vaccine. Equivalent immunogenicity was defined as a serum hemagglutinin inhibition (HAI) geometric mean titer (GMT) ratio >0.5 and <2.0 for each of the 3 vaccine-specific strains. A total of 376 subjects 5–8 years and 566 subjects 9–49 years of age were evaluable. Postvaccination HAI GMTs were equivalent for CAIV-T and LAIV. The GMT ratios of CAIV-T/LAIV for the H1N1, H3N2, and B strains, respectively, were 1.24, 1.02, and 1.00 in the 5- to 8-year-old group and 1.14, 1.12, and 0.96 in the 9- to 49-year-old group. Seroresponse/seroconversion rates (4-fold rise) were similar in both age groups for each of the 3 vaccine strains. Within 28 days, the most frequent reactogenicity event in both groups was runny nose/nasal congestion, which occurred at a higher rate after dose 1 (44% and 42%, respectively) than dose 2 (41% and 29%, respectively) in the 5- to 8-year-old group. Otherwise, rates of adverse events (AEs) were similar between treatment groups and age cohorts, with no serious AEs related to study vaccine. The immunogenicity, reactogenicity events, and AEs were comparable for refrigerated CAIV-T and frozen LAIV.