Swine flu is very much in everyone's mind these days and federal scientists have said that although they have "seed stock" of the virus available with them to develop a swine flu vaccine they have many questions unanswered before they can get to the job.

The questions range from how many vaccines would be needed to when it should be produced. World Health Organization officials said the although preparedness for a potential flu pandemic is more than it was five years ago it would still take months before it would be readily available.

Dr. Richard Besser, acting director of the Centers for Disease Control and Prevention said the seasonal vaccine that is currently being used would not have any effect on the swine flu that is doing the rounds. There have been 28 confirmed cases in New York with 20 others in four other states.

According to infectious-disease specialist P. J. Brennan, chief medical officer for the University of Pennsylvania Health System, the current vaccine making is a multi step process that begins in the molecular biology labs of international and national health organizations such as the Centers for Disease Control and Prevention.

"To have vaccines ready, you really have to be preparing six to eight months in advance," Brennan said.

Wayne Marasco, associate professor of medicine in the department of cancer immunology and AIDS at the Dana-Farber Cancer Institute at Harvard agrees that making a vaccine for this entirely new strain of flu could take months."You can't pull an old virus off the shelf and say it's 95% similar and hope to get cross-protection."

Dr. Anne Schuchat, director of the CDC's national immunization center, said the agency is considering three major options for the fall vaccine where the options are a swine flu only vaccine, substituting one of the three strains in the seasonal vaccine with a swine flu dose or adding swine flu as a fourth strain to the vaccine, creating a four-tiered - or "quadrivalent" - flu vaccine.

The option selection depends on the behavior of the virus and Besser and other public health experts said that no one is certain what the H1N1 swine strain is doing.

Experts are unsure if it will continue to trigger clusters of cases slowly as it is now, or speed up. "We're concerned and we're expecting things to change," said. Schuchat.

Schuchat said the CDC and WHO are in talks with the vaccine industry. Donna Cary, spokeswoman for the leading vaccine manufacturer in the United States, Sonofi-Pasteur said, "The FDA would have to approve it before the vaccine could be administered in the United States. There would have to be some kind of quality testing to make sure we have something that won't make people sick."

She added that it takes at least four to six months to produce the annual flu vaccine and it's impossible to tell how long it would take to produce all the vaccine until the company has all the genetic details of the virus in question.