The nasal spray, Schaffner explains, is a "tamed virus." In this case, it has been engineered to multiply in the nose, but it can't get down into the rest of the body because the rest of the body is a degree or two warmer than the nose, and the virus is incapable of multiplying at that higher temperature.
"It's a miracle of modern science," he said.
However, the nasal spray form of the flu vaccine may leave someone symptomatic for a day with a runny nose and a sore throat.
"That's a small price to pay, in my opinion," said Schaffner.
"This is a very good question and a question we don't know all the answers to," said Dr. Erica Brownfield, an associate professor of medicine at Emory University School of Medicine.
But while medicine may not be able to tell us if stress increases the risk of catching a cold or the flu, stress can make either of those conditions worse once you have it.
"What we do know is that those people who are under chronic stress are probably more likely to develop complications from a cold or the flu," said Brownfield.
While people may need to relax once they're sick, the anxiety of putting yourself at higher risk isn't worth adding to an already stressful lifestyle.
"For those individuals who have acute stress in their life, they shouldn't be concerned about developing more colds and flu under typical circumstances," said Brownfield.
"No, being out in the cold or being cold or having wet clothes does not increase your chance of having a cold or the flu," said Dr. Jon Abramson, chairman of the department of pediatrics at Wake Forest University Baptist Medical Center.
"This is one of the myths that do exist both about the common cold or the flu, and clearly from a lot of studies this is not the case."
Since this myth persists, the likely reason behind it is the rise in cases once the temperature drops in the United States.
"It is true, however, [that] the flu virus circulates mainly in the fall and the wintertime, and that therefore, you do see a lot more flu during that time than the rest of the year in temperate countries, such as the United States," said Abramson.
While the viruses are more common during these times of the year, the consensus among physicians seems to be that this is caused by people staying indoors to avoid the cold -- not from the cold itself.
Riding on an airplane may increase your flu risk, but it's not clear if it makes it any higher than do other crowded areas.
"I think anytime that you are in a crowd of people, the risk that you might catch a cold or catch the flu is increased. We tend to catch these illnesses from other people. And so when you're in a crowd, the likelihood that you'll come in contact with somebody who's infected naturally goes up," said Dr. Ronald Turner, a pediatrician at the University of Virginia School of Medicine.
Flu risk may be particularly elevated in these situations, because it is spread by germs in the air.