Swine Flu Shot Gives Fast Protection
H1N1 Swine Flu Vaccine Protects in 8-10 Days, U.S. Trials Confirm
Daniel J. DeNoon
WebMD Health News
Louise Chang, MD
Sept. 11, 2009 - You'll be protected from swine flu eight to 10 days after
getting a single shot of the H1N1 swine flu vaccine -- at least if you're a
healthy adult, U.S. studies show.
The Latest on
H1N1 Swine Flu
Learn about H1N1 swine flu:
Results of studies in children, who may still need two doses of the swine
flu vaccine, won't be available for two weeks. And it's still unclear whether
adults with chronic health conditions might need two shots of the pandemic flu
But the findings in adults amaze and delight health officials. The early
U.S. study results confirm yesterday's report from Australian studies that adults need only one standard dose of
H1N1 swine flu vaccine.
"Americans who get the H1N1 vaccine most likely will be protected sooner
than we thought," HHS Secretary Kathleen Sebelius said at a news conference
held to announce the findings. "Now it appears most people have a robust immune
response in eight to 10 days. It shortens the window of worry, and more people
can be protected much earlier."
The speedy immune response was so unexpected that researchers didn't even
bother to look for it in many clinical trial subjects. Some of the U.S. trials
didn't test for swine flu-neutralizing antibodies until 21 days after the first
shot. Fortunately, enough of them did.
Also surprising is how well the swine flu vaccine worked in the U.S.
studies. The H1N1 vaccines made by CSL and Sanofi raised protective levels of
antibody in 80% to 96% of adults aged 18 to 64 and in 50% to 60% of those over
"This is very good news for the H1N1 vaccine program," Anthony Fauci, MD,
director, of the U.S. National Institute of Allergy and Infectious Diseases,
said at the news conference. "There have been no significant adverse events
whatsoever. The vaccine is very well tolerated."
Swine Flu Race Is On
Now the race is on to get the swine flu vaccine into people's arms -- or
noses, as a FluMist inhaled version of the vaccine will be available. Swine flu
is now widespread in 11 states; all 50 states report cases.
Last week, nearly 60% of U.S. doctor visits were for flu-like symptoms, Anne
Schuchat, MD, director of the CDC's respiratory disease center, said at the
news conference. That means there's as much flu going around now as there was
at the peak of last flu season.
"These levels of influenza activity are extremely unusual for this time of
year," Schuchat said. "Ninety-eight percent of the viruses are novel H1N1."
Fauci said plans are still on track to start distributing some 45 million
doses of swine flu vaccine in mid-October. About 20 million more doses are
expected to become available every week after that. The U.S. has purchased 195
million doses in all. That now looks like more than enough to vaccinate every
American who wants it.
Vaccine supplies could be extended even further. By giving the vaccine along
with an immune-boosting substance called an adjuvant, the Australian studies
show, just one half-dose of vaccine works as well as a full dose without
Unfortunately, these adjuvants have not yet been approved by the U.S. FDA.
This means they will not be used in the U.S. during this flu season. But
adjuvant is approved in Europe and elsewhere, and should greatly extend the
worldwide supply of swine flu vaccine.
SOURCES: HHS news conference, Sept. 11, 2009, with:
- Kathleen Sebelius, secretary, U.S. Department of Health and Human Services
- Anthony Fauci, MD, director, National Institute of Allergy & Infectious Diseases, NIH
- Jesse Goodman, MD, director, Center for Biologics Evaluation and Research, FDA
- Anne Schuchat, MD, director, National Center for Immunization and Respiratory Diseases, CDC
Clark, T.W. The New England Journal of Medicine, published online Sept. 10, 2009.
Greenberg, M.E. The New England Journal of Medicine, published online Sept. 10, 2009.
WebMD Health News: "1 Swine Flu Shot Enough?"
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