Ferrets are the closest animal to humans when it comes to being infected with influenza.The ferrets received a 3.75, 7.5, or 15 microgram dose of the 2009 H1N1 virus-like particle vaccine or a placebo and were boosted with a second dose after three weeks, the company said in a statement.Researchers at the CDC infected the animals with H1N1 taken from a California patient.