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A safe, effective vaccine against the 2009 pandemic influenza A (H1N1) virus is badly needed. Given that most people do not have cross-reactive antibodies against this new virus (JW Infect Dis Sep 16 2009), experts have speculated that vaccine-induced immunity would require higher doses, a two-dose series, or an adjuvanted vaccine. Now, in an industry-sponsored trial involving 240 healthy adults in Australia (half aged 18–49, and half 50–64), researchers have compared the safety and immunogenicity of two different doses of 2009 H1N1 hemagglutinin antigen.
Participants were randomized to receive either 15 or 30 µg of hemagglutinin antigen intramuscularly; antibody titers were determined at baseline and 21 days postvaccination. Antibody titers…