H1N1 vaccine expected in mid-October

Healthy adults need only a single dose of H1N1 flu vaccine to protect against infection, officials announced on Friday during a Health and Human Services Department briefing. Previous guidance suggested that two shots were required.

"[This] shortens the window of worry, and more people can be protected much earlier," said Health and Human Services Secretary Kathleen Sebelius in her opening remarks, adding the available vaccines will go further and cover more people.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health, said adults in clinical trials showed strong immune responses to single vaccine doses. Trials are still under way for children and pregnant women.

The Centers for Disease Control and Prevention will partner with the Food and Drug Administration on a surveillance program to monitor individuals who receive the vaccine to identify any potentially negative long-term reactions. Agency officials will collect vaccine safety data from insurance companies and electronic medical records to quickly pinpoint problems.

Forty million doses of the H1N1 vaccine are expected to be released around Oct. 15. Recipients are protected relatively soon after the first dose, and the vaccine will be distributed as quickly as possible ahead of the epidemic's peak.

Children and young adults are particularly susceptible to the H1N1 virus, while seniors are a priority group for the seasonal flu vaccine. Thirty-eight million of the 115 million seasonal flu vaccine doses already are available from health care providers and pharmacies.