Denver ? Public health officials say Americans should roll up their sleeves for a dose of reality: For most of us, getting a flu shot is not a life-or-death matter.

The flu vaccine will not necessarily prevent you from experiencing the flu’s miserable symptoms, like fever, hacking cough, runny nose and “hit-by-a-truck” body aches. Studies have shown that the shot generally works about 52 percent of the time.

If you are elderly or chronically ill, the vaccine can help jump-start your body’s weakened defenses and perhaps prevent the worst from happening if you do catch the virus.

But the millions of people who are younger and healthier do not really need it — especially during a vaccine shortage, public health officials say.

“Right now the entire country runs on fear and we don’t need to live like that,” said Catharine A. Kopac, a Georgetown University gerontology nurse. “We somehow think we should be disease-free all the time. If you’re leading a healthy life and you get sick with the flu, you’re probably going to get through it.”

For years, most people ignored the government’s vaccination campaign, in part because of persistent myths that the shot hurts (not much; the needle is small) and it makes you sick (no, the conventional vaccine is made from dead virus).

As recently as last year, 4 million doses of vaccine went unused, even though an alarming early strain of influenza emerged and gained attention because several children died from it, particularly in Colorado.

Passengers board the Victoria Clipper high-speed ferry from Seattle to Victoria, British Columbia. Many aboard the ship had booked the 2 1/2-hour voyage to get a flu shot at the Canadian ferry terminal, a package deal offered by the ferry company at a discounted price. Monday's sailing, which normally operates at 1/3 capacity this time of year, was sold out, with approximately 330 people making the trip.

Two-thirds of Americans age 65 and older were vaccinated in 2002. But only 28 percent of people with chronic illness and 30 percent of children 6 months to 23 months old got their shots.

Nevertheless, the vaccine shortage this fall is igniting a “scarcity mentality” similar to runs on banks during stock market crashes and convenience stores when hurricanes brew offshore.

Millions who never bothered to get vaccinated before suddenly are hounding their doctors, workplace nurses and supermarket clinics. Americans are crossing borders and proffering their exposed arms; in Seattle, people are paying $105 to ride a high-speed ferry for a shot at the dock in Victoria, British Columbia.

What is behind this feverish behavior? Researchers say it is not so much the flu itself as a more generalized sense of feeling unprotected.

“Not being able to get the shot takes away your control over your health,” said David Ropeik, director of risk communication at the Harvard School of Public. “That sense of being out of control is scary.”