Influenza ("flu") is a contagious disease that spreads around the United States every year, usually between October and May. Flu is caused by influenza viruses, and is spread mainly by coughing, sneezing and close contact.
Anyone can get flu. Flu strikes suddenly and can last several days. Symptoms vary by age, but can include:
Flu can also lead to pneumonia and blood infections, and cause diarrhea and seizures in children. If you have a medical condition, such as heart or lung disease, flu can make it worse.
Flu is more dangerous for some people. Infants and young children, people 65 years of age and older, pregnant women, and people with certain health conditions or a weakened immune system are at greatest risk.
Each year thousands of people in the United States die from flu, and many more are hospitalized.
Flu vaccine can:
Q: When and how often should I get vaccinated?
A: Everyone 6 months and older should get a flu vaccine every year by the end of October. It takes about two weeks after vaccination for the body’s immune response to fully respond and for you to be protected, so make plans to get vaccinated.
Q: What viruses do this season's flu vaccines protect against?
A: There are many flu viruses, and they are constantly changing. The composition of U.S. flu vaccines is reviewed annually and updated to match circulating flu viruses. Flu vaccines protect against the three or four viruses (depending on the type of flu vaccine) that research suggests will be most common. For this flu season, three-component vaccines are recommended to contain:
Four component vaccines are recommended to include the same three viruses above, plus an additional B virus called B/Phuket/3073/2013-like virus (B/Yamagata lineage).
Q: Will the flu vaccine last all season?
A: When most healthy people with regular immune systems are vaccinated, their bodies produce antibodies, and they are protected throughout the flu season, even as antibody levels decline over time. Older people and others with weakened immune systems may not generate the same amount of antibodies after vaccination; further, their antibody levels may drop more quickly when compared to young, healthy people.
For everyone, getting vaccinated each year provides the best protection against the flu throughout flu season. It’s important to get a flu vaccine every season, even if you got vaccinated the season before and the viruses in the vaccine have not changed for the current season.
Q: Can I get a flu vaccine if I am allergic to eggs?
A: People who have experienced only hives after exposure to eggs can get any licensed and recommended flu vaccine that is otherwise appropriate for their age and health.
People who have symptoms other than hives after exposure to eggs, such as angioedema, respiratory distress, lightheadedness or recurrent emesis - or who have needed epinephrine or another emergency medical intervention - also can get any licensed and recommended flu vaccine that is otherwise appropriate for their age and health, but the vaccine should be given in a medical setting and be supervised by a health care provider who is able to recognize and manage severe allergic conditions. (Settings include hospitals, clinics, health departments and physician offices). People with egg allergies no longer have to wait 30 minutes after receiving their vaccine.
Q: When should I get the flu shot?
A: Getting vaccinated before flu activity begins helps protect you once the flu season starts in your community. It takes about two weeks after vaccination for the body’s immune response to fully respond and for you to be protected, so make plans to get vaccinated. CDC recommends that people get a flu vaccine by the end of October, if possible. Children aged 6 months through 8 years who need two doses of vaccine should get the first dose as soon as possible to allow time to get the second dose before the start of flu season. The two doses should be given at least 28 days apart.
Q: How well will flu vaccines work this season?
A: Influenza vaccine effectiveness (VE) can vary from year-to-year among different age and risk groups and even by vaccine type. How well the vaccine works can depend in part on the match between the vaccine virus used to produce the vaccine and the circulating viruses that season. It’s not possible to predict what viruses will be most predominant during the upcoming season. CDC monitors circulating viruses throughout the year and provides new and updated information about the vaccine match as it becomes available.
Q: Can the flu vaccine provide protection even if it isn't a good match to the circulating virus?
A: Yes, antibodies made in response to vaccination with one flu virus can sometimes provide protection against different but related viruses. A less than ideal match may result in reduced vaccine effectiveness against the virus that is different from what is in the flu vaccine, but it can still provide some protection against flu illness.
Q: Can I get vaccinated and still get the flu?
A: Yes. It’s possible to get sick with the flu even if you have been vaccinated (although you won’t know for sure unless you get a flu test). This is possible for the following reasons:
Q: Can I get the nasal spray in place of the shot?
A: Only injectable flu shots are recommended this season. Live attenuated influenza vaccine (LAIV) – or the nasal spray vaccine – is not recommended for use during this season because of concerns about its effectiveness.
Q: Can I get the flu vaccine if I am pregnant?
A: Yes, but not the live intranasal. Changes in your immune, heart and lung functions during pregnancy make you more likely to get seriously ill from the flu. Catching the flu also increases your chances for serious problems for your developing baby, including premature labor and delivery. Get the flu shot if you are pregnant during flu season; it’s the best way to protect yourself and your baby for several months after birth from flu-related complications.
Q: Is there anything that I need to do different if I am 65 years of age or older?
A: Human immune defenses become weaker with age, which places older people at greater risk of severe illness from influenza. Also, aging decreases the body’s ability to have a good immune response after getting influenza vaccine. A higher dose of antigen in the vaccine is supposed to give older people a better immune response, and therefore, better protection against flu. Data from clinical trials comparing Fluzone to Fluzone High-Dose among persons aged 65 years or older indicate that a stronger immune response (i.e., higher antibody levels) occurs after vaccination with Fluzone High-Dose. Whether or not the improved immune response leads to greater protection has been the topic on ongoing research. Fluzone High-Dose is approved for use in people 65 years of age and older. As with all flu vaccines, Fluzone High-Dose is not recommended for people who have had a severe reaction to the flu vaccine in the past.
Q: Will the flu vaccine protect me from the stomach flu such as diarrhea or vomiting?
A: The flu vaccine will not protect you from the stomach flu or virus. The flu vaccine protects against the respiratory flu.
For more information, please contact your healthcare provider.