vaccine for the H1N1 swine flu

FRIDAY, July 17 (HealthDay News) -- U.S. health officials said Friday that development of a vaccine for the H1N1 swine flu is on track, with the first doses possibly ready by the fall.

Initial tests of a vaccine are expected to start soon, possibly within weeks, although results about its safety and effectiveness won't be known for about month after that, officials said.

Secretary of Health and Human Services Kathleen Sebelius has announced plans for a voluntary vaccination program in the fall, "assuming availability of a safe and effective vaccine," Dr. Anne Schuchat, director of the National Center for Immunization and Respiratory Diseases at the U.S. Centers for Disease Control and Prevention, said during a midday press conference.

Schuchat said the CDC is working with states and local governments to develop vaccination programs. On July 29, the CDC's advisory committee for immunization practices will meet to discuss who should receive the H1N1 vaccine. The committee also will look at who should be vaccinated first -- for example, health-care workers -- if the vaccine is in short supply.

"We think things are proceeding well," Dr. Jesse Goodman, the U.S. Food and Drug Administration's acting chief scientist and deputy commissioner, said during the press conference. "We expect initial trials to be starting very shortly."

As vaccine development continues, the H1N1 swine flu virus continues to sweep around the world.

"This virus is not going away," Schuchat said, adding that it's still causing infections in the United States in the summer, "in temperature and humidity conditions that are not very favorable to seasonal influenza virus transmission."

On Friday, the CDC was reporting 40,617 confirmed cases of H1N1 infection and 263 deaths, although officials believe more than 1 million Americans have been stricken with the swine flu. The reason for the disparity: The virus continues to produce mild symptoms and patients typically recover quickly.

Schuchat said she expects to see a new outbreak of H1N1 swine flu in the United States in the fall. It will most likely start earlier than seasonal flu, she said. Seasonal flu typically surfaces in late fall.

Unlike seasonal flu, the H1N1 flu continues to pose more problems for younger people, Schuchat added. "There are a higher attack rates and hospitalizations in younger adults and children," she said.

In the Southern Hemisphere, where the winter flu season is under way, cases of H1N1 virus infection are being reported, along with cases of seasonal flu, Schuchat said. "In the reports we have, the virus continues to affect generally younger people, sparing the elderly to a great extent," she said.

And, as in the United States, the H1N1 virus is causing severe respiratory problems in the Southern Hemisphere, a trend that's unique to the new strain of flu and not seen in seasonal flu, Schuchat noted. "We've heard of intensive-care units with many younger people who have this new H1N1 virus."

Last month, researchers reported in the New England Journal of Medicine that, unlike seasonal flu, the new H1N1 flu strain attacks younger people and can be more severe and deadly in that group.

One report focused on the initial flu outbreak last spring in Mexico that included 2,155 cases of swine flu reported by the end of April. Researchers zeroed in on the 100 people who died and what caused those deaths. They found that 87 percent of the deaths and 71 percent of the cases of pneumonia were seen in people aged 5 to 59. That's unlike what is seen with seasonal flu epidemics, in which, on average, 17 percent of those in that age range who are seriously ill die and 32 percent develop severe pneumonia, the researchers said.

Also Friday, the World Health Organization said it would no longer keep a global tally of individual cases of H1N1 swine flu. The reason: The pandemic is circling the globe at an "unprecedented" speed, and keeping a count no longer serves a valuable purpose.

Instead, the agency said it would focus on new countries experiencing infections, with an eye out for genetic mutations that could mean the virus is becoming more virulent and potentially more dangerous.

Before it stopped reporting individual cases, the WHO had listed almost 95,000 cases and 429 deaths worldwide.