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Frequently Asked Questions - Vaccine

When does flu season start and end?

Flu season varies from year to year, but it can begin as early as October and last as late as May. Generally speaking, the season peaks in January or February.

How long does the flu vaccination work for?

The flu vaccine will protect you for one flu season. It is designed to protect you from the strains of influenza that are expected to circulate during that season.

Why should people get vaccinated against the flu?

Influenza is a serious disease that can lead to hospitalization and even death. Even healthy people can get very ill and spread influenza to others.

Why do I need to get an influenza vaccination annually?

The viruses that cause influenza are constantly changing. It’s not unusual for new viruses to appear each year, so the vaccine is formulated annually to keep up with the changing viruses.

Why is getting a shot every year so important?

Influenza is a serious, sometimes fatal disease. Everyone who is at least six months of age should get the vaccine. It’s especially important for some people to get vaccinated. People who are at high risk of developing serious complications like pneumonia include patients with medical conditions like asthma, diabetes, heart or kidney disease, a weakened immune system, and chronic lung disease. Also in that group are pregnant women and people 65 years and older. It’s also important that people who live or care for others who are high risk get the vaccine; this includes household contacts and caregivers of the people listed above.

I got a flu shot last year. Do I need another one this year?

Yes! Since the vaccine is only good for one flu season, it’s important to get vaccinated annually. Even if the viruses don’t change from year-to-year, the body’s immunity to influenza viruses declines over time.

I had the flu last year. So I now have immunity, right?

Not necessarily! Even if a person gets influenza, studies show that immunity to influenza viruses, whether they are acquired through natural infection or vaccination, declines over time.

Can I get the flu from the flu vaccination?

NO! You cannot get influenza from the flu shot or nasal spray. The shot contains inactivated (killed) influenza viruses that cannot cause illness. The nasal spray contains weakened live viruses that can only cause mild infections in the cooler temperatures found in the nose. The viruses cannot infect the lungs or other areas in the body where warmer temperatures exist.

Can I get the flu vaccination if I am sick?

If you have a moderate-to-severe illness with a fever, you should wait until you are better to get the vaccine. If you have a low grade fever or mild illness (runny nose, watery eye, slight stomach upset) it is OK to go ahead and receive the flu shot.

How does the flu vaccination work?

Influenza vaccines (the flu shot or the nasal spray) cause antibodies to develop in the body. These antibodies provide protection against infection with the viruses that are in the vaccine.

Can I get the flu even though I got a flu vaccination this year?

Yes! The ability of flu vaccine to protect a person depends on two things: 1) the age and health status of the person being vaccinated, and 2) the similarity (“match”) between the virus strains in the vaccine and those circulating in the community. If the match is good, vaccine effectiveness is higher, but if the match isn’t close, the effectiveness can be reduced. It’s important to remember, though, that even if there isn’t a close match, the vaccine can still protect many people and prevent flu-related complications because antibodies made in response to the vaccine can provide some protection (cross-protection) against different, but related strains of influenza viruses.

What types/strains of flu are covered in this year's vaccination?

The 2015-2016 flu vaccine protects against:

  • A/California/7/2009 (H1N1) pdm09-like virus
  • A/Switzerland/9715293/2013 (H3N2)-like virus
  • B/Phuket/3073/2013-like virus (B/Yamagata lineage)
  • B/Brisbane/60/2008-like virus (B/Victoria lineage vaccine virus)

Does the flu vaccination work right away?

No! It takes about two weeks after the vaccination for antibodies to develop in the body and provide protection against the influenza viruses. In the meantime, people are still at risk for getting the flu. That’s why it’s better to get vaccinated early in the fall, before the flu season really gets under way.

What are side effects of receiving the flu vaccination?

The viruses in the flu shot are killed, so you cannot get the flu from the shot. Minor side effects that could occur are soreness, redness, or swelling where the shot was given, a mild fever, or body aches. These usually last one to two days. On very rare occasions, the vaccine can cause serious problems such as severe allergic reactions.

The viruses in the nasal spray are weakened and in children can cause runny nose, wheezing, headache, vomiting, muscle aches, and fever. Adults who get the spray can get runny nose, headache, sore throat, and cough.

What are the medical contraindications to getting a shot?

Talk to your health care provider if you have:

  • A severe allergy to eggs
  • A history of severe reaction to a flu vaccination
  • A moderate-to-severe illness with a fever
  • A history of Guillain-Barre’ Syndrome (a severe paralytic illness, also called GBS)

For more information, visit www.cdc.gov/flu/.