By Rob Stein
Washington Post Staff Writer
Friday, September 11, 2009 2:34 PM
The swine flu vaccine appears to work for adults with just one shot and within 10 days, a major boost to the widespread immunization campaign that officials are planning to protect people against the first influenza pandemic in 41 years, researchers reported.
Preliminary data from an Australian study found that a single standard dose could produce an immune response in more than 96 percent of recipients, and U.S. studies indicate that the protection occurs within eight to 10 days, scientists reported. The vaccine also appeared safe.
The eagerly awaited findings mark the first results from a flurry of studies that scientists have been rushing to conduct to develop a swine flu vaccine. The findings indicate that plans to inoculate millions of Americans -- the most ambitious vaccine campaign in U.S. history -- and worldwide could occur much more quickly and require far less vaccine than officials had feared.
"This is good news," said Anthony S. Fauci of the National Institutes of Health, which is leading the U.S. efforts to develop the vaccine. "This is very good news. If you needed two doses, that would be a major strain on vaccine supplies nationally and globally."
In a statement released Friday, officials said U.S. studies found a 15-microgram dose of vaccine made by Sanofi Pasteur produced a protective immune response in 96 percent of adults aged 18 to 64 and in 56 percent of adults aged 65 and older. The same single dose of the CSL vaccine in the Australian study produced a protective immune response in 80 percent of adults aged 18 to 64 and in 60 percent of adults aged 65 and older. Officials said the differences may be due to "technical differences" in the preliminary data.
"This is very encouraging news," said Health and Human Services Secretary Kathleen Sebelius as a briefing outlining the findings began, noting it means more Americans will be protected sooner than had been thought. "The vaccine we have purchased will go further and cover more people," Sebelius said.
Results from additional studies will be needed to see whether children and other special groups need one or two doses, he added. Young children usually need two seasonal flu shots because they have not been exposed to the virus before.
The National Institutes of Health is conducting a series of studies testing the swine flu vaccine on 4,600 volunteers, including adults, children and pregnant women.
"We will hopefully get some information about kids from our trial in a couple of weeks," Fauci said.
The results from CSL Ltd. in Australia will be published in the New England Journal of Medicine but were released online Thursday because of their urgency. The study involved a standard dose of 15 micrograms of vaccine and found that the vaccine produced a strong immune response in more than 96 percent of the subjects.
"The concern that people had was that because this was a new virus that this would require two doses for everyone. That would have created a problem of supply," Fauci said. "This greatly alleviates the problem of supply."
The findings also mean that adults will not have to return for a booster shot, which would have greatly complicated the already daunting vaccine effort.
The results were welcomed by officials at the World Health Organization, which has been particularly concerned about providing enough vaccine to poorer countries.
"If this is true, this is quite encouraging," said Gregory Hartl, a WHO spokesman. "If you only need one shot instead of two, the vaccine will go twice as far. Twice as many people will be able to get the vaccine."
The Australian findings were released with a second study from the University of Leicester. In that study, 175 British volunteers ages 18 to 50 received another version of the vaccine made by Novartis Corp. -- either 7.5 or 15 micrograms of vaccine, along with a substance known as an adjuvant, which can boost a vaccine's effectiveness. The study found that either dose produced adequate immune response within 14 days. Adjuvants have been used widely in Europe, which could extend the supplies even further. U.S. officials were considering approving an adjuvant in this country if supplies ran low.
The strong immune response was somewhat puzzling, Fauci said, especially given the results of a third paper, from the federal Centers for Disease Control and Prevention, that found exposure to the seasonal flu vaccine offered no protection against the swine flu.
"The responses you're seeing suggest that somehow or other there has been some previous exposure to similar viruses or some vaccine that is responsible," Fauci said.
The new virus, known as H1N1, emerged last spring in Mexico and quickly spread around the world, causing at least 2,837 deaths, including at least 556 in the United States so far and prompting the WHO to declare the first influenza pandemic since 1968.
The pandemic has sparked a flurry of emergency planning, including a rushed program to develop a vaccine. Because the virus is new, experts thought most people would need one shot followed by a booster several weeks later to produce sufficient protection.
Because the first batches of vaccine are not expected until mid-October, that meant the first Americans would not be protected until after the outbreak might have peaked.
The federal government has already spent $2 billion to buy 195 million doses of vaccine and plans to purchase enough to vaccinate every American if necessary.
Unlike the typical flu, the H1N1 virus has been affecting children and young adults much more often than the seasonal flu.
As a result, the top priority for vaccination will be everyone age 6 months to 24 years and people who care for children younger than 6. Pregnant women, health-care workers and adults ages 25 to 64 with health problems that put them at risk for complications are also being given high priority.
The results from the H1N1 vaccine trials came as top U.S. health officials urged Americans to get vaccinated against the seasonal flu.