Influenza, the dreaded cold-weather virus, was once believed be brought on by the influence of the stars. Although that particular flu myth has been dispelled, doctors still battle others about the flu and its vaccine each season.
"Flu myth busting is the most difficult thing I do," said Dr. Len Horovitz, pulmonary specialist at Lenox Hill Hospital in New York City.
From how you get the flu to how you fight it off to concerns over the safety of the seasonal flu vaccine, there's a lot of misinformation out there that may leave people underprotected for flu season, doctors say.
ABC News asked experts to set the record straight on 15 hard-to-shake flu myths.
Despite the continual urging by the Centers for Disease Control and Prevention that all Americans over the age of 6 months should be vaccinated against the seasonal flu, only 30 to 55 percent of eligible people in the U.S. got vaccinated in 2010, according to CDC data. Much of this lag in vaccination rates stems from lingering fears over the safety of the vaccine.
This fear began in 1979, when live-virus vaccines were used and people did get sick from them, says Horovitz. "That was the start of people deciding they weren't going to get a flu shot," he says.
But today, injectable flu vaccine uses dead virus and "is made up of only parts of the flu virus, so it cannot in any way give you the flu," says Dr. William Schaffner, chairman of Preventive Medicine at Vanderbilt University Medical Center. While the nasal spray variety of the vaccine uses a live, weakened virus, it can only multiply in the colder environment of the nose and can't give you the actual, full-blown flu. Sometimes people have a sore throat and runny nose for a day, but not the actual flu, Schaffner says.
One reason that this myth persists is that flu vaccine causes a brief fever in about 1 percent of recipients, which leads some to worry that they are actually getting the flu after getting the vaccine. "These are very transient and rare reactions," Schaffner says, and do not indicate that the patient has the flu.
Another issue is that it can take several weeks for the vaccine to cause the buildup of enough antibodies in the body to become effective, "so it is quite possible to get the flu soon after getting vaccinated, which could lead to this misunderstanding," says John Barry, author of "The Great Influenza."
The flu vaccine is given in the hundreds of millions of doses every year and is "extraordinarily safe," Schaffner says. Other doctors echo this sentiment -- that the flu itself is the threat, not the vaccine.
There are very rare risks associated with any vaccine, notes Dr. Christian Sandrock, a physician and an expert in infectious disease at the University of California Davis Medical Center, but it's about weighing the benefits of vaccine against the risk.
"What is far more dangerous is taking the risk that you will get infected with flu if not vaccinated," says David Topham, co-director of the New York Influenza Center of Excellence. "Flu infection kills almost 40,000 people each year in the U.S. alone. Flu vaccine does not kill anyone."