By Kelly Brewington | email@example.com
September 12, 2009
Twice as many adults could get the swine flu vaccine as scientists initially expected because the inoculation works in just one dose instead of two, federal officials announced Friday.
The preliminary data from American clinical trials of a vaccine come as a surprise and a relief to public health experts who feared there would not be enough vaccine to reach everyone who would need it.
The data confirm results from an Australian study released Thursday that also found that one dose is effective.
"This is very good news for the vaccination program, both with regard to the supply of the vaccine and its potential efficacy," said Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health. The agency is funding the American trials of two vaccines, one from drugmaker Sanofi Pasteur and another from CSL Ltd.
In the Sanofi vaccine tests, NIH scientists found that 96 percent of healthy adults ages 18 to 64 developed an immune response just eight days after receiving one 15-microgram shot. The percentage was lower in the elderly - 56 percent in people 65 and older. The CSL vaccine yielded similar results - 80 percent of adults 18 to 64 developed an immune response with one 15-microgram dose, while 60 percent of adults 65 and older did.
Fauci said researchers were not surprised that the elderly developed less of an immune response - the figures were similar to the response found when the elderly are given the seasonal flu shot. "Of course, we want to study that - can we ever make that better?" he said. "But it's right now right in the ballpark of what is the immune response in elderly individuals."
The data come from studies being conducted at the University of Maryland's Center for Vaccine Development and a handful of other academic centers nationwide that began testing the experimental vaccine on adults and children last month in a race to launch a mass vaccination campaign expected to start in mid-October.
Developing a safe and effective vaccine is crucial in the government's fight against the pandemic, which began with outbreaks in Mexico this spring and has killed 593 people nationwide - 3,205 around the globe - according to estimates by the federal Centers for Disease Control and Prevention and the World Health Organization.
Infectious disease experts have warned of an onslaught of the virus this fall and are bracing for the possibility that it could mutate and become deadlier.
Federal officials would not offer specifics about how the newest findings could alter the logistics of a vaccination campaign. The government has spent more than $1 billion for about 190 million doses of the vaccine from five manufacturers. Roughly 40 million doses are expected to be ready by the middle of next month and would be released as they become available.
The preliminary results of the Australian study, published in the New England Journal of Medicine, were similar to the American trials. Australian researchers found that 97 percent of the 240 adults who got one 15-microgram dose developed antibodies to the virus after just 10 days.
The trials were done by vaccine maker CSL, which is licensed to provide millions of doses of the vaccine in the United States.
Using less vaccine means not only being able to stretch supply farther, but it also means cutting down on costs and the frustrating logistics of lining people up for two shots, said Dr. Wilbur Chen, a vaccinologist who is helping to oversee the H1N1 vaccine trials at the University of Maryland's Center for Vaccine Development.
"I was elated when I found out the results," he said. "That was one of the best-case scenarios, seeing this vaccine working in people this well. We can rest much better at night, knowing that we will have more doses and we'll have an easier time to vaccinate the population. It was a headache, honestly, thinking about vaccinating people twice in 21 days. It's hard enough to get people to come back."
The initial trial results leave many unanswered questions. Scientists don't yet know whether one dose will be effective in children or pregnant women - the vaccine is still being tested in the groups. Results in children aren't expected for another two weeks and findings in pregnant women may not come until late October, Fauci said.
It's also unclear whether people with compromised immune systems would benefit from one dose rather than two. That group, along with children and pregnant women, should be at the front of the line for being vaccinated, since they are at most risk for developing serious complications from the virus, the CDC has said.
Researchers are examining ways to further stretch vaccine supply. Chen is heading an NIH-sponsored trial on a vaccine with an immune booster added to it, known as adjuvant, starting Monday at the university.
Using an adjuvant - a substance with an oil and water base that is added to the vaccine - could mean having four times as much vaccine supply, Chen said. But adjuvants, used with flu vaccines in Europe, are not licensed for flu vaccines here. Federal approval would require an emergency declaration by the Food and Drug Administration.
Still, Chen thinks studying adjuvants now could prove helpful later in the flu season or in future years.
"Depending how bad H1N1 gets, we may want to stretch out our vaccine supply even further," he said. "This study still addresses a critical issue that is important for public health planning as we get into the flu season."
In addition, no one knows if the vaccine will have adverse effects on people in the long term. So far, the trials done at academic centers nationwide have not shown any immediate problems, other than minor swelling at the site of the shot and arm soreness, Fauci said.
Federal officials said they have stepped up monitoring for possible adverse reactions down the road, specifically, a rare neurological disorder called Guillain-Barre syndrome. After a 1976 outbreak of a different swine flu, the government launched a vaccination effort but some reports found the vaccine increased the risk of Guillain-Barre, which can be fatal.
"It's on people's minds," said Dr. Anne Schuchat, director of the CDC's National Center for Immunization and Respiratory Diseases. "It's a very rare condition, but it's something we want to be ready for. We might see more Guillain-Barre this fall, because we'll expect to see more flu this fall. We want to know if the vaccine has any kind of link to that. We don't expect that. But we want to be on the lookout."
A stronger vaccine for swine flu•Eighty percent to 97 percent of healthy adults exhibited immune response after one dose of swine flu vaccine in three separate studies, preliminary data showed.
•The vaccines were not as effective among the elderly, with about 60 percent showing an immune response.
•Testing continues of children and pregnant women to see whether they will require one or two doses.