Reporter: Silvia Castaneda

Doctors are startled at just how sick some people here in Nashville have become from the smallpox vaccine. The vaccine is being tested at Vanderbilt, and President Bush could announce at any time just who needs the vaccine and when. When he does, just how worried should you be about the side effects? News 2's Silvia Castaneda showed us what local volunteers are going through.

Jennifer Doersam is a lab assistant working on the smallpox vaccine study. She's also gotten the vaccine herself.

"My arm was just very sore and I had a little bit of trouble using it, but otherwise I functioned perfectly well," Doersam said.

Vanderbilt researchers said that is the typical reaction to the vaccine.

What isn't so typical is Bedford County paramedic Brian Bruce's experience that went on for days.

"Headaches, body aches, you know. On a one to ten pain scale, I had pain at an eight," said Bruce.

Side effects from the vaccine also include fatigue, swelling, and rashes. In a previous study, those side effects were so severe, a third of volunteers had to stay home from work or school for at least a day.

While side effects are of concern, Vanderbilt researchers said these symptoms are also expected, and so far, no worse case scenarios: a death from the vaccine, which is rare.

So as plans to vaccinate Americans against the potential biological weapon grow near:

"I would tell the public to be prudent and cautious, but not to panic because of this vaccine. A lot of what we see today, we saw 30 years ago. It's just that it's a different culture and we're not used to seeing that," said Dr. Tom Talbot.

So what's the worst side-effect case that's been seen at Vanderbilt? It was a volunteer who had bouts of vomiting. She couldn't eat or drink anything, so she became dehydrated. After treatment, however, she recovered and is doing fine.