Swine Flu Trials Continue to Point to 1-Dose Vaccine

Sept. 12 -- FRIDAY, Sept. 11 (HealthDay News) -- U.S. health officials said Friday that additional trials of the H1N1 swine flu vaccine continue to find that a single dose produces a strong immune response in healthy adults.

The findings confirm study results released Thursday out of Australia and Britain that found that a single dose of the vaccine creates enough antibodies to protect against the virus within about 10 days.

Despite the encouraging news about the vaccine, the officials noted that flu activity is unusually high for this time of the year, and virtually all of the infections are coming from the H1N1 swine flu strain.

The first 45 million doses of the H1N1 vaccine aren't expected until mid-October. And results of trials of the vaccine in young children and pregnant women -- two of the groups high on the vaccine priority list -- won't be available for several more weeks, officials said.

"We are encouraged by the data we've seen both in other countries and here in the United States," Kathleen Sebelius, secretary of the U.S. Department of Health and Human Services, said during an afternoon press conference.

"It appears we will need only one dose for most healthy adults and the vaccine we are producing is working extremely well," she said. "That is critically important news."

It had been thought that two shots would be needed to provide full immunity to the virus. A one-dose regimen would greatly expand the supply of vaccine and hasten individual immunity.

In the trial results released Friday, 96 percent of healthy adults between the ages of 18 and 64 had a strong immune response to the 15-microgram dose of the vaccine produced by drug maker Sanofi Pasteur. The response rate to the 15-microgram vaccine made by CSL Limited was 80 percent, said the officials, who downplayed the difference in the response rates.

Sebelius also said the 15-microgram vaccine acts faster than had been anticipated, so people will be protected sooner after getting their shot. "It appears that most folks have a robust immune response in eight to 10 days, which is very positive news," she said. "The vaccine that we have purchased will go further and help us cover more people."