The World Health Organization says several laboratories around the world are developing a vaccination against swine influenza A-H1N1. The organization has raised its alert to level five, just below declaring the flu virus outbreak to be a pandemic. The process of vaccine development can take months.
  

Electron micrograph of swine flu virus

Vaccine trials are being conducted

As the number of cases grows, so do efforts to develop a vaccine for swine influenza A-H1N1.

Dr. Wilbur Chen, who conducted vaccine trials for the avian flu at the University of Maryland, is among scientists who monitor animal flu viruses that move to humans. We found him at a vaccine research convention in Baltimore, Maryland.

"We, as vaccine researchers, in this field also would like to move the whole technology forward so we could create vaccines really, really quickly," Dr. Chen said.

Trials will take time to develop

Ed Mocarski

But the process of developing a vaccine could take three months, maybe more. Scientists begin by injecting live virus into fertilized chicken eggs, and then they wait.

The U.S. Centers for Disease Control has already isolated a sample of the virus and has grown what's called a seed stock. A seed stock is a strain of the virus that's the first step toward growing a vaccine.

"We have people who are very interested in the flu, as you can imagine," says Ed Mocarski, chief scientist with Medimmune, a company that produces vaccines.

"It has to be tested in animal models to make sure it's safe to go ahead into people," he explained. "And make sure it is live attenuated [disabled virus] and not have some capacity to cause disease."

Balancing benefits and risk of side-effects

It is a delicate balance between speed and the risk of side-effects from the vaccine. Scientists are still haunted by the U.S. massive vaccination program against a swine flu outbreak in 1976. Although a pandemic did not develop, about 30 people died of a neurological disorder thought to be linked to the vaccine.

"The risk of having some reactions that might just be transient, maybe just a couple days of pain or fever, I think would be outweighed by the potential lives saved -- if a virus were really moving through a population rapidly," Dr. Chen stated.

Dr. Robert Belshe

The dosage is determined at human clinical trials. Dr. Robert Belshe runs a vaccine development unit at St. Louis University's, School of Medicine. "It will take a number of months to produce the vaccine and do clinical trials with it," Dr. Belshe said. "Can we do it between now and the Fall? I'm sure vaccine manufacturers are busy now, figuring out what their timeline is and how much vaccine they can produce in the next few months."

Mocarski says they are. "All the companies who are prepared in flu manufacturing would be prepared to rise to that need," he said.

Vaccine research is global effort

The World Health Organization says several laboratories worldwide are working on a vaccine.

Experts say swine flu could slowly diminish now, only to re-emerge later this year. So scientists need to decide if that danger is great enough to include the new virus in the general flu vaccine this fall.

Dr. Wilbur Chen

"We typically have our annual influenza vaccine that has three viral components in it," Dr. Chen explained. These are the viruses we think will circulate next year, and they've already been selected."

Scientists say any determination is not foolproof because the flu is fickle.

"Influenza is unpredictable and that's the only thing we can count on," Dr. Belshe said.

For now, the World Health Organization has advised all countries to activate their pandemic preparedness plan.