Trial of Influenza A (H1N1) 2009 Monovalent MF59-Adjuvanted Vaccine — Preliminary Report

Abstract

Results of an interim analysis of the responses to the 7.5-μg dose of MF59-adjuvanted vaccine by days 14 and 21 are presented (data from four of the seven groups studied, for a total of 100 subjects). The most frequent local and systemic reactions were pain at the injection site and muscle aches, noted in 70% and 42% of subjects, respectively. Two subjects reported fever, with a temperature of 38°C or higher, after the first dos- ing. Antibody titers, expressed as geometric means, were generally higher at day 14 among subjects who had received two 7.5-μg doses of the MF59-adjuvanted vaccine than among those who had received only one by this time point (P = 0.04 by the he- magglutination-inhibition assay and P<0.001 by the microneutralization assay). By 21 days after vaccination with the first dose of 7.5 μg of MF59-adjuvanted vaccine, the rates of seroconversion, as measured with the use of a hemagglutination-inhibition assay and a microneutralization assay, were 76% and 92% of subjects, respectively, who had received only one dose to date (with the second dose scheduled for day 21) and 88 to 92% and 92 to 96% of subjects, respectively, who had already received both doses (P = 0.11 and P = 0.64, respectively). Conclusions In preliminary analyses, the monovalent influenza A (H1N1) 2009 MF59-adjuvant- ed vaccine generates antibody responses likely to be associated with protection within 14 days after a single dose is administered. (ClinicalTrials.gov number, NCT00943358.)