September 11, 2009 — Initial results from National Institutes of Health trials corroborate and reinforce findings released yesterday that a single dose of the influenza A (H1N1) vaccine is well-tolerated and produces a protective response in adults, government officials announced today during a press conference.
Blood samples from volunteers showed a robust response at "the rather early time point," of 8 to 10 days after the first 15-μg dose from the Sanofi Pasteur vaccine. That response happened in 96% of adults aged 18 to 64 years and in 56% of adults 65 years and older, said Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases.
A similar dose of a vaccine from CSL Limited produced a robust response in 80% of people 18 to 64 years old and 60% of adults aged 65 years and older, the officials said.
"This is very good news for the vaccination program, both with regard to the supply of vaccine as well as to its potential efficacy," Dr. Fauci said. He said the lesser response in elderly people is similar to what happens with the seasonal flu shots.
Asked about recent studies suggesting that the H1N1 pandemic may peak in the United States before the vaccine is available in mid-October, Dr. Fauci noted that it is possible that some vaccine may be available earlier.
Anne Schuchat, MD, from the Centers for Disease Control and Prevention, told reporters, "We wish we knew exactly what was going to happen in every community in the United States over the next several months. Disease is increasing already, and it's a bit of a race to get the vaccine to be available as quickly as possible ahead of the disease. But remember that this is not going to be exactly the same in every community."
She said officials do believe there will be prevention opportunities, particularly with the news that adults may be protected "relatively promptly after the first dose."
Saying that current levels of influenza activity are extremely unusual for this time of year, Dr. Schuchat added that 98% of the influenza virus circulating is the H1N1 strain. She indicated there is influenza activity in all 50 states and the District of Columbia, with widespread activity in 11 states.
The increase is mainly in children and young adults, as it was with the H1N1 outbreak last spring and summer, she said.
The officials said federal agencies will be looking for any adverse events from the H1N1 vaccine through a number of systems, including some enhanced surveillance methods. Dr. Schuchat said the Centers for Disease Control and Prevention plans to set up a new surveillance system for Guillain-Barré syndrome through a number of state health departments.
The Centers for Disease Control and Prevention is expecting 115 million doses of seasonal influenza vaccine to be available, and it is already in physicians' offices, clinics, and pharmacies. But Dr. Schuchat explained that there may not be enough in all locations as the season unfolds. She added that it is appropriate to administer the seasonal influenza vaccine now, although the season will likely last through May.
Health and Human Services Secretary Kathleen Sebelius, who introduced the speakers at the press conference, announced that she had received the seasonal influenza vaccination today.