The race is on to create a vaccine for swine flu, as many infectious disease experts warn that the northern hemisphere could face a "second wave" of H1N1. But some worry the fast-tracked vaccine may be more dangerous than the virus itself.

Across Europe, Asia and the U.S., vaccine manufacturers have begun testing the first batches of the vaccines, with volunteers rolling up their sleeves to try the new formulations for safety and effectiveness. They will be testing different dosages, looking to see if any trigger immune reactions or other possible side effects.

But in his office in Winnipeg, University of Manitoba medical ethicist Dr. Arthur Schafer is worried.

"We're rushing the vaccines, there isn't time for them to be properly tested for effectiveness; there won't be time for them to be properly tested for safety," he tells CTV News.

The vaccine is being touted as our best weapon against the virus, and hailed as a sort of "magic bullet." But Schafer notes that the first scientific data will only provide information on the correct dosage and immediate reactions from the shot. Long-term safety data won't be available when vaccination programs begin in the fall.

"So the claim that we know it to be safe and effective just isn't levelling with the Canadian public. No one knows that," says Schafer.

Many remember the ill-advised mass vaccination program in the U.S. in 1976, when millions of Americans and some Canadians got a vaccine for a virus that quickly fizzled out. About 4,000 people became ill after getting immunized, including about 500 who came down with Guillain-Barré syndrome, a paralyzing though generally temporary neuromuscular disorder.

When anger over the vaccine program reached a crescendo, the program was quickly withdrawn and the U.S. government was left with a $3-billion lawsuit.

The World Health Organization has acknowledged safety issues "will inevitably arise during a pandemic when vaccine is administered on a massive scale. For example, adverse events too rare to show up even in a large clinical trial may become apparent when very large numbers of people receive a pandemic vaccine."

Still, Schafer says he's not comfortable with the plan to encourage every Canadian to get the vaccine. He recently let his feelings be known in an interview with the Winnipeg Free Press and says his comments seemed to hit a nerve.

"I've had a lot of feedback from scientists around the country who have emailed or phoned to say they are relieved someone is flagging these concerns," he says.

Shafer says the evidence from the southern hemisphere suggests swine flu is no more lethal than the seasonal flu. So he wonders why a mass vaccination program is being considered.

"There are serious public health issues and issues of ethics as to whether we should be distributing (vaccines) massively to healthy people, including children and pregnant women, when there are really big question marks about their effectiveness and their safety."

But Toronto vaccine specialist Dr. Allison McGeer says speeding the vaccine through production and testing is necessary.

She says as the safety data comes in, in the coming weeks, and a clearer picture of swine flu's effects in the southern hemisphere emerges, decisions will be made about who needs it.

"The order is insurance," she said, referring to the vaccine.

McGeer agrees that open public discussion is needed. She points out that there are risks to any influenza, including swine flu. The vaccine is designed to protect those at risk.

"The recommendation is based on a very careful assessment of what the risks of influenza are, and what the benefits (and risks) of the vaccine are."

With a report from CTV Medical Specialist Avis Favaro