Flu shot: Your best bet for avoiding influenza

This year's annual flu shot will offer protection against H1N1 flu (swine flu) virus, in addition to two other influenza viruses that are expected to be in circulation this flu season. A new vaccine that protects against four strains of the virus will also be available, as will a high-dose flu vaccine for adults age 65 and older.

Influenza is a respiratory infection that can cause serious complications, particularly to young children and to older adults. Flu shots are the most effective way to prevent influenza and its complications. The Centers for Disease Control and Prevention (CDC) recommends that everyone 6 months of age or older be vaccinated annually against influenza.

Here are the answers to common questions about flu shots.

Because the flu vaccine is produced by private manufacturers, its availability depends on when production is completed. For the 2013-2014 flu season, manufacturers have indicated shipments are likely to begin in August and continue throughout September and October until all vaccine is distributed. Doctors and nurses are encouraged to begin vaccinating their patients as soon as flu vaccine is available in their areas.

It takes up to two weeks to build immunity after a flu shot, but you can benefit from the vaccine even if you don't get it until after flu season starts.

New flu vaccines are released every year to keep up with rapidly adapting flu viruses. Because flu viruses evolve so quickly, last year's vaccine may not protect you from this year's viruses.

After vaccination, your immune system produces antibodies that will protect you from the vaccine viruses. In general, though, antibody levels start to decline over time — another reason to get a flu shot every year.

The CDC recommends annual influenza vaccinations for everyone age 6 months or older. Vaccination is especially important for people at high risk of influenza complications, including:

Pregnant womenOlder adultsYoung children

Chronic medical conditions can also increase your risk of influenza complications. Examples include:

AsthmaCancer or cancer treatmentChronic obstructive pulmonary disease (COPD)Cystic fibrosisDiabetesHIV/AIDSKidney or liver diseaseObesity

Check with your doctor before receiving a flu vaccine if:

You're allergic to eggs. Some flu vaccines contain tiny amounts of egg proteins. If you have an egg allergy or sensitivity, you'll likely be able to receive a flu vaccine — but you might need to take special precautions, such as waiting in the doctor's office for at least 30 minutes after vaccination in case of a reaction. There's also a flu vaccine that doesn't contain egg proteins, Food and Drug Administration (FDA) approved for use in people age 18 and older. Consult your doctor about your options.You had a severe reaction to a previous flu vaccine. The flu vaccine isn't recommended for anyone who had a severe reaction to a previous flu vaccine. Check with your doctor first, though. Some reactions might not be related to the vaccine.