In the Northern Hemisphere the flu (Medically referred to as influenza) season generally runs from November to April, with most cases occurring between late December and early March, but the flu, or anti-flu, vaccine is usually offered between September and mid-November.
The flu is highly infectious and is a serious viral respiratory infection and every year in the United States, on average:
5% to 20% of the population gets the flu
About 36,000 people die from the flu or its complications.
More than 200,000 people are hospitalized from flu complications.
Flu vaccines are routinely available for seasonal influenza, but these vaccines are not likely to be protective against the H1N1 Virus.
The U.S. Centers for Disease Control and Prevention recommends that people who are at risk for serious complications from the flu be vaccinated each year. Adults with asthma are at high risk of developing complications after contracting the influenza virus, as respiratory infections like influenza are more serious in patients with asthma, and such infections can often lead to pneumonia and acute respiratory disease.
There are two types of seasonal flu vaccines, the injection (with killed virus) and nasal spray vaccines (containing live, but weakened, virus).
1/ The "flu shot", an inactivated vaccine (containing killed virus) that is given with a needle, usually in the arm. The flu shot is approved for use in people older than 6 months, including healthy people and people with chronic medical conditions.
2/ The nasal-spray flu vaccine, a vaccine made with live, weakened flu viruses that do not cause the flu (sometimes called LAIV for "live attenuated influenza vaccine" or FluMist®). LAIV (FluMist®) is approved for use in healthy people 2-49 years of age who are not pregnant.
Who SHOULD receive the flu vaccine
Everyone 50 years of age or older
Children aged 6 months to 18 years old
Police, firefighters, and other public safety workers
Out-of-home caregivers and household contacts of anyone in any of the high-risk groups
Children and adolescents (aged 6 months to 18 years) receiving long-term aspirin therapy
Residents of nursing homes and other facilities that care for people with chronic medical conditions
Persons who want to reduce the risk of becoming ill with influenza or of transmitting influenza to others
Health care workers and other employees of hospitals, nursing homes, and chronic care and other outpatient facilities who care for patients
Those planning to travel to the tropics at any time or to the Southern Hemisphere from April through September who did not receive a flu vaccine the previous year
People who have chronic lung or heart disorders, and/or chronic diseases such as diabetes mellitus, kidney disease, severe anemia, or immune deficiency (including HIV/AIDS)
People who should NOT get a flu shot include:
Anyone with a fever
Infants under 6 months old
Anyone who has ever had a severe reaction to a flu vaccination.
Anyone with Guillain-Barre syndrome (GBS), a rare condition that affects the immune system and nerves
People severely allergic to eggs and egg products (ingredients for flu shots are grown inside eggs, so tell your doctor if your child is allergic to eggs or egg products before he or she gets a flu shot)
When should you get influenza vaccine
The viruses that cause influenza change often, and protection declines within a year after vaccination. So people who need the vaccine should get it every year. The vaccine begins to protect you after 1 to 2 weeks and protection may last up to one year.
What are the risks from influenza vaccine
There is a very small risk that serious problems, even death, could occur after taking the vaccine. The risk from the vaccine is much smaller than the risk from the disease. Serious problems from the flu vaccine are rare. Side effects from the flu vaccine may include: soreness, redness, or swelling where the shot was given; fever; aches and pains. More information on the Types of Flu Shot Reactions.
How Effective is the Flu Shot
The effectiveness of the flu vaccine is dependent upon the extent of the match between the virus strains used to prepare the vaccine and those viruses in actual circulation. The age and health status of the individual also play a role in determining the effectiveness of the vaccine.
The Centers for Disease Control and Prevention (CDC) often will recommend that certain high-risk groups be given priority when flu shot supplies are limited.