Swine Flu Shots May Come Too Late to Stem Fall Outbreak: Study

Sept. 11 -- THURSDAY, Sept. 10 (HealthDay News) -- The height of this year's fall H1N1 swine flu outbreak is expected in October, but a planned vaccine may arrive too late to stop it, a new study suggests.

The first batch of the new H1N1 vaccine, totaling only 45 million doses, is not expected before mid-October, according to the U.S. Centers for Disease Control and Prevention. Clinical trials are still underway, and on Wednesday the U.S. National Institutes of Health announced it had just begun its trials of the vaccine in one high-risk group, pregnant women.

So, a vaccine arrival date of mid-October may be too little, too late. Because even if a vaccine were available in time, 70 percent of the U.S. population would need to be vaccinated to stop the spread of this pandemic virus, the study authors projected.

"If the H1N1 flu follows the pattern we are expecting we should see a sizable outbreak in the U.S. starting in early September and probably peaking in mid- to late- October," said lead researcher Ira Longini, a professor of biostatistics at the University of Washington in Seattle.

A vaccine is the best way to stem the epidemic, Longini said. "However, in the current situation we could come up short," he said. "It looks like we will be too late if everything stays the same."

The CDC has already reported that the number of H1N1 cases is already on the rise in the United States, particularly in the Southeast where school opened early, and on college campuses.

But infections with the H1N1 virus continue to be mild, producing symptoms typical of run-of-the-mill seasonal flu.

Although the vaccine may not be all that helpful to curb a fall epidemic, it is still important to get vaccinated, Longini said. That's because the H1N1 flu is expected to linger in the population for at least 20 years, with new outbreaks occurring this coming winter and spring, and for years to come.

The report is published in the Sept. 10 online edition of Science.