BACKGROUND
When the novel H1N1 influenza A strain appeared in April of 2009, development of novel H1N1 vaccines became a public health priority.
METHODS
We conducted a phase‐2, multicenter, randomized, placebo‐controlled, observer‐blind clinical trial of a 2009 H1N1 vaccine in 1313 young (age, 18-64 years) and older (age, >or=65 years) adults. Participants were randomized 1:4:4:4 to receive 2...