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Abstract
Data are needed from large clinical trials of paediatric, adult, and elderly people
to find the appropriate antigen dose and vaccination schedule for the 2009 pandemic
influenza A H1N1. We therefore report preliminary safety and immunogenicity results
after one injection of a licensed monovalent pandemic H1N1 vaccine in the USA.
We randomly assigned healthy children (aged 6-35 months and 3-9 years) and adults
(18-64 years and >or=65 years) to vaccine containing per dose 7.5 microg (children
and adults), 15 microg (children and adults), or 30 microg (adults only) haemagglutinin
in two placebo-controlled, observer-masked, multicentre phase 2 studies done in the
USA. Participants were allocated with an interactive voice-response system or computer-generated
randomisation lists with opaque scratchable patches. Primary outcome was haemagglutination
inhibition antibody response 21 days after the first of two planned vaccinations (interim
analysis of studies in progress). Analyses were by full-analysis set. The trials are
registered with ClinicalTrials.gov as NCT00953524 and NCT00952419.
410 of 423 children and 724 of 750 adults given an active vaccine, and 50 of 51 children
and 95 of 99 adults given placebo were assessed for immunogenicity on day 21. After
active vaccination, 45 of 101 (45%; 95% CI 35-55) to 47 of 94 (50%; 40-61) infants
aged 6-35 months, 75 of 109 (69%; 59-77) to 80 of 106 (75%; 66-83) 3-9-year-old children,
134 of 141 (95%; 90-98) to 144 of 144 (100%; 98-100) of 18-64-year-old adults, and
93 of 100 (93%; 86-96) to 93 of 98 (95%; 89-98) elderly adults were seroprotected
(proportion with titres >or=1:40). No vaccine-related serious adverse events occurred.
Injection-site and systemic reactions were reported by up to about 50% of every age
and vaccine group, with no noticeable differences between vaccine and placebo groups.
One dose of vaccine was highly immunogenic in adults, suggesting that it afforded
sufficient protection against this pandemic influenza A H1N1 virus. Two doses of vaccine
will probably be needed in children younger than 9 years. Safety and reactogenicity
of the vaccine were acceptable and similar to those of seasonal vaccine.
Office of the Assistant Secretary for Preparedness and Response, and Biomedical Advanced
Research and Development Authority.
Copyright 2010 Elsevier Ltd. All rights reserved.