Since we’re right in the middle of flu shot season, here are the answers to a few questions you might be mulling over on your way to get your injection of this year’s vaccine cocktail.

How long have flu shots been around?

The flu has been making us sick since at least 1580, when a major pandemic ripped through Europe and Asia, killing ten percent of Rome’s population in a single week. Over a dozen pandemics have struck since then, but it wasn’t until the 1930s that scientists actually identified the influenza virus as the cause of all this illness. One of the foremost researchers in the country, Dr. Thomas Francis, Jr., used ferrets to show that the illness was purely viral.

Once scientists found the culprit, Francis and his colleagues started working to find a cure. In 1941, they discovered a substance in the noses of people with colds that neutralized the virus and realized that recovering from the flu kick-started the immune system. By 1944, Francis’ team had developed a working flu vaccine for the Army, and it soon became available to civilian patients.

Who were the guinea pigs for these first vaccines?

In 1943, Francis and his colleagues thought they had a working vaccine, but they needed test subjects. Who better to use than convicts? The first study of the vaccine’s effectiveness centered on 200 inmates at the Ypsilanti (Michigan) State Hospital, where the shots seemed safe and effective. The drug then made its way to a larger national test population of 12,500; during the next flu outbreak, the unvaccinated population got the flu at a rate four times higher than their counterparts who had taken the shots.

Did any other big names work on that first vaccine?

Yup. One of Francis’ star researchers was a hotshot young virologist named Jonas Salk, who went on to perfect the polio vaccine in 1955.

How would, say, Gerald Ford fight swine flu?

Glad you asked. There was another small outbreak of swine flu back in 1976, and President Ford sprang into action. Although there were only a handful of confirmed cases of the flu – all of them soldiers at Fort Dix, New Jersey – Ford ordered a flu shot for every single person in the country. It seemed like a good idea at the time; vaccinating the entire population could have headed off another pandemic like the one that shook the country in 1918.

There were more than a few problems with Ford’s master plan, though. The particular vaccine that went out for this program had the potentially terrible consequence of triggering the development of the nerve disease Guillain-Barre syndrome. In the first two months of the program, 500 vaccinated people developed Guillain-Barre, which damages the peripheral nervous system and can lead to paralysis; over 25 of these patients died from complications related to the disease.

While the flu was frightening, a potentially lethal or paralyzing nerve disease was even scarier to a lot of Americans. Support for Ford’s mandatory vaccination program waned, and even though the First Family televised their own shots to allay the country’s fears, public support for the program dropped off. In the end, the government pulled the plug on the vaccinations in December 1976, after 40 million Americans had been vaccinated.

So is Guillain-Barre still a worry for flu shot recipients?

Not really. While that 1976 swine flu virus vaccine was associated with Guillain-Barre, the CDC says that only one study of all the vaccines since has turned up any connection between a flu shot and GBS, and that study placed the risk of GBS at roughly one in a million.

Why do I have to get a new flu shot each year?

There are a couple of reasons. First, each year’s seasonal flu shot contains three types of flu that the CDC, the FDA, and the World Health Organization think might be prevalent that year. These types, one A (H3N2) virus, one A (H1N1) virus, and one B virus, change from year to year. Furthermore, even if the virus types didn’t change from year to year, the immunity offered by last year’s flu shot would be somewhat weakened, so you’d want to top it off.

Why should I get vaccinated right now?

Because even if you get the vaccine today, you can still get the flu tomorrow. According to the CDC, it takes about two weeks for the flu vaccine to really kick in and build up your antibodies to the point where you’re protected from infection. In the meantime, the flu can still drop its hammer on you. To fight this lag time, the CDC recommends that you get your flu shot early in the fall before flu season gets rolling.

Why does my doctor care if I’m allergic to eggs?

Because dead flu viruses don’t just grow on trees. In order to obtain dead viruses for use in flu shots, scientists have to grown the viruses themselves. The vast majority of these viruses are grown using fertilized chicken eggs.

There’s hope if you’re allergic to eggs, though. The federal government is supporting the drug company Novartis with almost $500 million in funding to create a new flu vaccine factory in Holly Springs, NC. The drug Novartis hopes to produce there, Optaflu, is novel because it comes from mammalian cell cultures rather than eggs. The facility could be ready to roll as early as 2010.

Can nasal spray vaccines make you or your family sick?

If you’re afraid of needles, 2003 was a big year for you. That’s when pharmaceutical company MedImmune introduced FluMist, a nasal spray alternative to the traditional flu shot. Whereas traditional shots gave patients dead flu viruses to build up antibodies, FluMist gave the needle-phobic a dose of living—albeit severely weakened—flu virus.

This sort of vaccine, which is known as a live attenuated vaccine, raised some eyebrows from worriers. If you were getting live flu virus, couldn’t that make you sick or contagious to those around you? Probably not. Researchers at the Mayo Clinic concluded that while patients who had taken FluMist did shed some of the virus to their surroundings, it was a negligible amount that wouldn’t infect an adult. While children were more susceptible, the New York Times researched the question and concluded that the overall likelihood of transmitting the flu virus after taking FluMist was only 2.5 percent.

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