By far, the single best way to prevent the flu is for individuals, especially persons at high risk for serious complications from the flu, to get a flu shot each fall. Influenza can be prevented with a high degree of success when a person receives the current influenza vaccine or influenza shot. This vaccine is made each year so that the vaccine can contain influenza viruses that are expected to cause illness that year.

At the first sign of influenza symptoms see your doctor. Some doctors use a new rapid point of care test given in a doctors office which can diagnose all strains of influenza A and B. Many physicians now use antiviral medications when they are confident of the diagnosis. You can get the vaccine at your doctor's office or a local clinic, and in many communities at workplaces, supermarkets, and drugstores. You must get the vaccine every year because it changes.

The viruses in the vaccine are inactivated so that someone vaccinated cannot get influenza from the vaccine. Instead the person vaccinated develops protection in his or her body in the form of substances called antibodies.

Scientists make a different vaccine every year because the strains of flu viruses change from year to year. Nine to 10 months before the flu season begins, they prepare a new vaccine made from inactivated (killed) flu viruses. Because the viruses are killed, they cannot cause infections. The vaccine preparation is based on the strains of the flu viruses that are in circulation at the time. It includes those A and B viruses (see section below on types of flu viruses) expected to circulate the following winter.

Sometimes, an unpredicted new strain may appear after the vaccine has been made and distributed to doctors and clinics. Because of this, even if you do get the flu vaccine, you still may get infected. If you do get infected, however, the disease usually is milder because the vaccine still will give you some protection.

Your immune system takes time to respond to the flu vaccine. Therefore, you should get vaccinated 6 to 8 weeks before flu season begins to prevent getting infected or reduce the severity of flu if you do get it. The vaccine itself cannot cause the flu, but you could become exposed to the virus by someone else and get infected soon after you are vaccinated.

October 15th to November 15th is the best time to get your influenza shot. Such a yearly vaccination has been found to be about 75 percent effective in preventing influenza. It may also reduce the severity of influenza and can be lifesaving. However, it's OK to get the shot earlier. Since the vaccine takes about 2 weeks to begin its effect. A later vaccination can also provide substantial protection. Until the flu season is over, it's never "too late" to get a flu shot.

The influenza shot is covered by Medicare and some other health plans.

Anyone who wants to lower their chances of getting the flu (the shot can be administered to children as young as 6 months) can get a flu shot. Persons who provide essential community services (such as police, firemen, etc.) should consider getting a flu shot to minimize disruption of essential activities during flu outbreaks. Students or others in institutional settings (those who reside in dormitories) should be encouraged to get a flu shot.