By Tom Randall
June 26 (Bloomberg) --
The vaccine being developed to combat a pandemic of swine flu will require multiple shots to provide immunity from the new virus, and the added immunizations may overwhelm U.S. state agencies, health officials said.
Two injections will be required three weeks apart for swine flu, also known as H1N1, and a third will be needed for seasonal flu, health officials said at a meeting today at the U.S. Centers for Disease Control and Prevention, in Atlanta. Children younger than 9 years old will need four shots, the CDC said.
The U.S. government took the unusual step of purchasing all of the swine flu vaccine, and the shots probably will be administered through vaccine clinics set up by state health organizations, the CDC said. The agency estimates that at least 50 million vaccine doses will be available in the U.S. by Oct. 15, and enough vaccine to immunize everyone in the country will be available later in the season.
"Public health departments are under-funded and will get fatigued," said William Schaffner, an influenza expert at Vanderbilt University School of Medicine in Nashville, Tennessee, in an interview at the flu conference. "One shot probably gives you very little immunity, 10 to 20 percent at most."
Two state health-agency representatives said today that vaccinations would be slowed if states are responsible for administering shots instead of doctors' offices and pharmacies, said Jeanne Santoli, head of the CDC's routine vaccine distribution activities.
The CDC hasn't yet determined the role state agencies will play in disseminating the vaccine, and it will be working with states to ensure fast distribution, she said.
"Probably each state will decide what works best. There may be some states that lean toward the public sites and others that lean more toward the private," Santoli said.
Because swine flu is a new virus, most people have no natural immunity. The first shot provides an initial exposure, and the second shot boosts antibody levels in the body, Schaffner said.People older than age 50 are getting swine flu at far lower rates than younger people, evidence they may have some immunity from prior exposures to a similar virus, and will only need one shot, the CDC said.
Children under 9 have little immunity to any flu strain and need two shots for protection against seasonal flu, as well as two for swine flu, the CDC said. The agency is conducting tests to find the most effective dosing for different age groups.
The new flu is spreading at an epidemic rate earlier than the last two pandemics, in 1957 and 1968, Nancy Cox, director of CDC's flu division, said today in a presentation.
In those years, the virus emerged in late spring and subsided during the warmer summer months before picking up again in the fall.
The 2009 version is currently widespread across 11 states and circulating in parts of 19 others, according to a report presented yesterday at the CDC. (Note from Deanna...this is terribly out-dated information even according to the CDC's own updates!)
The number of seasonal flu cases has declined as swine flu spread after it was first identified in April.
"This new infectious disease is not going away," said Anne Schuchat, director of the CDC's Center for Immunization and Respiratory Diseases, in a conference call.
"In the U.S. we are seeing a steady increase in the number of reported cases. The number reported this week was the largest number reported so far in the outbreak."
A study conducted on ferrets at the CDC, presented today, found the swine flu virus may have symptoms that are more severe than those of seasonal flu and may be more difficult to transmit between people. The study is small and the results may not apply to humans, Cox said in an interview.
Ferrets are often used to study flu because the virus behaves in ferrets similarly to the way it does in humans, making the animal a good model, CDC spokesman Tom Skinner said in an interview.
Scientists have used laboratory tests to confirm 27,715 cases of swine flu in the U.S.,
(again, this is woefully behind the actual-to-date data from the CDC itself)
and as many as 1 million people may have been sick and not had testing, the CDC said.
One reason the swine flu vaccine may be administered through state health clinics is to allow the U.S. to closely track vaccine use and side effects.
In a 1976 outbreak of swine flu, some people who received the vaccine developed Guillain-Barre Syndrome, an autoimmune disorder that causes temporary full-body paralysis and may sometimes lead to death. The CDC estimates that 1 of every 100,000 people receiving the vaccines got the syndrome. Increased rates haven't been seen in other vaccines, and scientists still don't know what caused the link in 1976.
With rare side effects that occur in 1 in 100,000 patients or fewer, a state-run monitoring system is needed to collect enough data to alert health officials to problems with a new vaccine, the CDC said.
Companies working on swine flu vaccines include
Sanofi- Aventis SA, of Paris, GlaxoSmithKline Plc and AstraZeneca Plc, both based in London, CSL Ltd. of Melbourne and Novartis AG, of Basel, Switzerland.
To contact the reporter on this story: Tom Randall in New York at email@example.com.
Last Updated: June 26, 2009 16:11 EDT