Federal authorities plan to initiate a nationwide campaign in the coming weeks to persuade Americans to get the swine flu vaccine and to erase any public skepticism about the flu's danger and the safety of immunizations. Even as the Centers for Disease Control and Prevention has manufacturers working overtime to produce a vaccine for the swine flu by mid-October, government officials are concerned that demand for immunization will not be high. In particular, parents participating in focus groups this summer expressed concern that ramping up vaccine production would make it less safe than the seasonal flu vaccine.