Vaccine manufacturers are on track to deliver the first doses of the vaccine for pandemic H1N1 influenza in September, World Health Organization officials said today. The first batches will be limited, but larger deliveries are expected in October, Dr. Marie-Paule Kieny, director of the organization's Initiative for Vaccine Research said in a news conference in Geneva.
Kieny also noted that yields of antigen, the crucial component in vaccine production, are bigger than companies had initially expected, approaching the yields normally seen for seasonal flu vaccines. "I don't want to say too early that the question has been resolved, but it really seems like we have found a way to go round this problem," she said.
Several companies announced this week that they have begun human trials of the new vaccine against pandemic H1N1, commonly known as swine flu. Complete results will not be available from those trials until the end of this year or early next year. But researchers will be looking for any unusual reactions to the vaccine or other complications. Assuming none are seen, the Food and Drug Administration in the United States and health authorities in other countries are likely to approve the vaccines before the completion of clinical trials on the assumption that the new vaccine is basically the same as that for seasonal flu, just using a different strain of virus.
Kieny said the World Health Organization will work closely with member countries to monitor for severe side effects, such as Guillain Barre syndrome, a temporary paralysis disorder that disabled hundreds of Americans and killed 30 in the 1976 effort to control a different form of swine flu. Researchers now believe that side effect was caused by contaminants in the vaccine, and Kieny noted that vaccine-manufacturing techniques have improved substantially since then.
The key question that researchers are trying to resolve in the clinical trials is how many doses of the new vaccine will be required to provide sufficient protection against the virus. Preliminary studies have suggested that the antigen being used does not provoke as strong a response as that in the seasonal flu vaccine, and that it may be necessary to use two doses -- which would halve the total number of people who could be immunized. Some manufacturers in Europe are attempting to get around this problem by using vaccines with adjuvants -- chemicals that stimulate the body's immune system to react more strongly to the antigens in a vaccine. No flu vaccines containing an adjuvant have ever been approved in the United States, however.
The World Health Organization said Monday that 338 people had died from swine flu in the preceding week, bringing the global total to 1,154 deaths. The agency has stopped counting the number of laboratory-confirmed cases, but the actual number of those infected is believed to be in the millions. As of last Friday, the U.S. had reported 5,514 swine flu-related hospitalizations and 353 deaths.
-- Thomas H. Maugh II