Findings could expand vaccine supply and speed immunity, experts say
THURSDAY, Sept. 10 (HealthDay News) -- Preliminary tests of an H1N1 swine flu vaccine conducted in Australia and Britain show that a single dose creates enough antibodies to protect against the virus within about 10 days.
That's a potentially significant development, because it was thought that two shots would be needed to provide full immunity to the virus. A one-dose protocol would greatly expand the supply of vaccine and hasten individual immunity.
The H1N1 swine flu has already started to spread this fall in the United States and is infecting as many people now as would be expected in the peak of the flu season, according to the federal Centers for Disease Control and Prevention.
"A single vaccination at standard dose produced a strong immune response in more than 96 percent of adults studied," said the lead researcher of one of the two studies, Dr. Michael Greenberg, director of Clinical Development of Vaccines at CSL Behring, Ltd. in Victoria, Australia.
CSL is setting aside 36 million doses of its vaccine for distribution in the United States, Bloomberg News reported.
Most of the H1N1 pandemic planning in the world has assumed that two doses would be needed, Greenberg pointed out.
"At least in adults, this doesn't appear to be the case. This has important implications for public health policy as it would increase the number of people who could be vaccinated and also improve logistics by not having to bring most people back for a second shot, " he said.
For the trial, Greenberg and colleagues tested the vaccine in 240 people both under and over 50 years of age. These people were given two different doses of the vaccine and their antibody response was measured after 21 days.
The researchers found that a single dose of vaccine was enough to produce a sufficient number of antibodies to
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