"Homeland Security Secretary Janet Napolitano said Tuesday that pandemic flu probably will flare up soon after schools open in the fall, before vaccine is available. Napolitano also acknowledged that there would not be enough pandemic flu vaccine for everyone, at least in the early stages of the flu season. "There will be prioritization of vaccinations," she told members of the USA TODAY editorial board. . . . William Schaffner, a flu expert at Vanderbilt University, cautions that "flu is fickle" and there's no way to predict precisely how the coming flu season will unfold. One difference between swine flu and the 1957 version is that the new virus strikes a higher proportion of children and young people than the elderly. "If that holds, the group most vulnerable to the complications of influenza will continue to be spared," Schaffner says. "But H1N1 has a tremendous capacity to make children and young adults very sick."
In simple English - - if you were alive in 1957, you probably have some degree of protection or immunity due to exposure to the 1957 form of the virus. If you're younger than that, get the vaccine or have some Tamiflu in your medicine cabinet.