With school closings, a run on face masks, and even a flu-tracker iPhone app, it’s clear that swine flu is taking the country by storm.

As of this month, the flu, now called the 2009 H1N1 influenza, was widespread among people of all ages in 41 states, and it has been reported in all 50. Numbers of cases, hospitalizations, and deaths are unusually high for this time of year. And the situation is likely to get worse.

To stem the pandemic, the U.S. government is urging just about everyone older than 6 months to get the H1N1 vaccine as doses of the shot and nasal spray eventually become available for more than just high-risk groups.

Yet, while some people are waiting for hours in line to get themselves or their children vaccinated, others are avoiding it — convinced that the H1N1 vaccine is unnecessary or even unsafe. Scientists are fighting hard to tackle those misconceptions.

“These are urban myths and you can’t even track them down,” said Greg Poland, Director of the Mayo Clinic’s Vaccine Research Group in Rochester, Minn. “Someone says something that spreads virally from person to person and becomes truth in their minds.”

Here are expert answers to some of the most common concerns.

Concern #1: Swine flu is no big deal. It’s just another example of media hype.

Answer: H1N1 is a new strain of influenza that is significantly different from flu viruses that have circulated in previous years. As a result, doctors are seeing a larger than normal number of serious complications, including pneumonia and bacterial infections. They are seeing more cases and more complications than usual in healthy young people. And swine flu is hitting hard unusually early.

This time least year, seven people had died from influenza in the United States. So far this year, there have been about 1,000 deaths, including nearly 100 children, and about 10,000 flu-related hospitalizations. In a normal year, the seasonal flu virus kills an average of 36,000 people and sends more than 200,000 to the hospital. With mutations or other unpredictable events, H1N1 could end up being far worse.

Concern #2: The vaccine is more dangerous than the virus.

Answer: This stubborn myth drives the experts nuts. Rumors have been swirling around the H1N1 vaccine ever since the epidemic began. The truth is that the H1N1 vaccine is manufactured in exactly the same way as the seasonal flu vaccine, experts say, and six decades of experience support its safety. Like the seasonal flu vaccine, scientists expect the H1N1 vaccine to cut the risk of coming down with the flu by between 70 percent and 90 percent.

The vaccine contains no adjuvants — additives that can boost a drug’s effectiveness. It is available without the preservative thimerosal, which contains mercury and has raised health concerns even though no studies have linked it with any problems. You can’t get the flu from the vaccine. And more than a billion doses of the H1N1 vaccine have already been distributed without any unexpected side effects or other warning signs. (The only real risk is for people who are severely allergic to chicken eggs or other ingredients in the vaccine. Those allergies are rare.)

“All data point toward the fact that the vaccine is likely to be much safer than getting the disease,” said Neal Halsey, Director of the Institute for Vaccine Safety at the Johns Hopkins Bloomberg School of Public Health in Baltimore. “It should be a very simple decision to make. The safest thing to do is to get the vaccine.”

Concern #3: The government will force you to get the vaccine, no matter what you think about it.

Answer: This is simply not true, with just a few exceptions. Anyone in the military is required to be vaccinated as a security precaution. Some states are also mandating the vaccine for health-care workers. That’s already controversial. In states without the mandate, some health providers are actually choosing not to get it, despite evidence that they are more likely to contract and spread the disease if they remain unvaccinated. No one can force an ordinary civilian to get vaccinated.

Concern #4: I don’t need the vaccine because I’m young and healthy.

Answer: “The very people who say that are most at risk,” Poland said. If you’re young, you’re unlikely to have ever been exposed to a virus similar to H1N1, which means you probably don’t have a reservoir of defense proteins, or antibodies, equipped to fight it. In normal years, older people are most likely to experience complications from the flu, along with very young children. This year, people older than 60 are actually developing fewer problems than everyone else because their bodies have battled a larger variety of viruses over the years.

The benefit of the vaccine goes beyond a single person. Getting the vaccine not only keeps you healthy. It also protects your co-workers, your friends, your family, and your kids.

“I can’t stress enough that not getting the vaccine is not a risk-free option,” Poland said. “By the numbers, it is far riskier than any theoretical risk or fear of the vaccine.”