Swine flu vaccination

A nurse prepares a swine flu vaccination to administer to people who volunteer to get it at a subway station in Mexico City, Tuesday Jan. 31, 2012. Federal Health Secretary Salomon Chertorivski Woldenberg said Tuesday there have been 1,623 cases of all strains of flu in Mexico so far in January, 90 percent of them H1N1. That's the version that originally was called swine flu when it caused pandemic that started in Mexico in 2009. (AP Photo/Eduardo Verdugo)