If the government decided to go ahead with a national swine flu immunization campaign, there literally was no time to waste. It would take months to make the vaccine and eight to ten weeks to distribute it nationally, the first time ever that so many people would be receiving a vaccine. It takes two weeks for a vaccinated person to become immune to the flu. And so the time from the manufacture of a swine flu vaccine to the successful immunization of most of the nation was going to be at least three months.