Government officials are worried that, despite their best efforts, people won’t get a shot to protect themselves against swine flu. A recent survey suggests that only 40 percent of Americans said they were sure they would line up for the vaccine. Authorities are shocked at the tepid response. "It's surprising numbers are as low as they are," one researcher said. Some expressed optimism that those who say they do not want to be vaccinated will be convinced. One proponent told The Washington Post, "If the early acceptors show up, and they have a good experience, as more vaccine comes in some of the skeptics may be persuaded to come in and take advantage themselves."