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What to Expect from an H1N1 Vaccine
August 24, 2009 - 5:00 AM | by: Jonathan Serrie
An effective vaccine against the H1N1 virus is expected to become available to the general public this fall. But federal health officials warn it's not a cure-all and are urging Americans to maintain good hygiene and coughing etiquette even after they're vaccinated.
CDC officials say they expect between 45 million and 52 million doses of vaccine by mid-October, followed by roughly 195 million doses by the end of the year.
Five manufacturers are producing vaccines -- an elaborate and time-consuming process that involves growing the virus inside specially-selected chicken eggs.
The CDC and its international counterparts have provided these manufacturers with new H1N1 strains in hopes they may be able to produce vaccines faster. The initial strains in use produce a fraction of the output of typical strains of seasonal flu.
H1N1 vaccines are undergoing human trials at eight locations around the country, including Emory University -- which is located next to the CDC's headquarters in Atlanta. Researchers hope to answer these fundamental questions:
* Will one dose of vaccine be enough to establish immunity to H1N1, or will patients require two?
* How large should each dose be: 15 or 30 micrograms?
* When is the best time to administer H1N1 vaccine: before, during or after a seasonal flu shot?
According to researchers, preliminary results from the trials, which began earlier this month, are promising.
"There are no red flags regarding safety," said Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases.
That gave researchers the go ahead to begin the first H1N1 vaccine trials on children last week. Trials on pregnant women are expected to begin in early September.
Also in September, researchers plan trials using adjuvants -- ingredients added to a vaccine to enhance its effectiveness. Health officials say adjuvants might be used in the event of severe shortages in vaccine supply, or if studies determine a particular additive produces a more effective immune response.
"We're keeping that on the table," said Jesse Goodman, MD, acting chief scientist and deputy commissioner for scientific and medical programs at the U.S. Food and Drug Administration. "We'll have the studies that will help inform what they do, including safety. But right now, our major initial focus is on the (current) licensed products and vaccines."
More than 4,500 Americans are expected to take part in the various human trials of H1N1 vaccines.
Although wide scale vaccination of the general public is expected in the fall, public health officials caution people not to let down their guard. While highly effective vaccines, such as the one for measles, can have success rates of 95 percent or better -- typical flu vaccines offer a protection level in the area of 70 to 80 percent, according to Goodman.
Also, humans take as much as two weeks to generate antibodies to flu after a vaccination. If two separate doses are required (a likely scenario, according to health experts) the lag time could be five weeks or longer before a patient develops immunity.
"People should not presume that the minute they're immunized, they're protected," Goodman said.
"That has important implications," Fauci added. "Even if you're vaccinated, wash those hands. Cover those coughs. Stay home if you're sick."
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