Flu Shot FAQ
Why should people get vaccinated against the flu?
Influenza is a serious disease that can lead to hospitalization and sometimes even death. Every flu season is different, and influenza infection can affect people differently. Even healthy people can get very sick from the flu and spread it to others. Over a period of 31 seasons between 1976 and 2007, estimates of flu-associated deaths in the United States range from a low of about 3,000 to a high of about 49,000 people. During a regular flu season, about 90 percent of deaths occur in people 65 years and older. The "seasonal flu season" in the United States can begin as early as October and last as late as May.
During this time, flu viruses are circulating in the population. An annual seasonal flu vaccine (either the flu shot or the nasal-spray flu vaccine) is the best way to reduce the chances that you will get seasonal flu and lessen the chance that you will spread it to others. When more people get vaccinated against the flu, less flu can spread through that community.
How do flu vaccines work?
Flu vaccines (the flu shot and the nasal-spray flu vaccine (LAIV)) cause antibodies to develop in the body about two weeks after vaccination. These antibodies provide protection against infection with the viruses that are in the vaccine.
The seasonal flu vaccine protects against three influenza viruses that research indicates will be most common during the upcoming season. Three kinds of influenza viruses commonly circulate among people today: influenza B viruses, influenza A (H1N1) viruses, and influenza A (H3N2) viruses. Each year, one flu virus of each kind is used to produce seasonal influenza vaccine.
Who Should Get Vaccinated This Season?
Everyone who is at least 6 months of age should get a flu vaccine this season. It's especially important for some people to get vaccinated. Those people include the following:
- People who are at high risk of developing serious complications like pneumonia if they get sick with the flu. This includes:
- People who have certain medical conditions including asthma, diabetes, and chronic lung disease.
- Pregnant women.
- People 65 years and older
- People who live with or care for others who are high risk of developing serious complications. This includes:
- household contacts and caregivers of people with certain medical conditions including asthma, diabetes, and chronic lung disease.
Is there anyone who should not get the vaccine?
Talk to your health care provider about vaccination if you have:
- A severe allergy to chicken eggs
- A history of severe reaction to a flu vaccination
- A moderate-to-severe illness with a fever (you should wait until you are better to get the vaccine)
- A history of Guillain–Barré Syndrome (a severe paralytic illness, also called GBS)
When Should I Get Vaccinated?
CDC recommends that people get vaccinated against influenza as soon as flu season vaccine becomes available in their community. Influenza seasons are unpredictable, and can begin as early as October.
It takes about two weeks after vaccination for antibodies to develop in the body and provide protection against the flu.
Flu vaccine is produced by private manufacturers, so availability depends on when production is completed. If everything goes as indicated by manufacturers, shipments are likely to begin in August and continue throughout September and October until all vaccine is distributed.
At this time, some vaccine providers may have exhausted their vaccine supplies, while others may have remaining supplies of vaccine. People seeking vaccination may need to call more than one provider to locate vaccine. The flu vaccine locator at http://vaccine.healthmap.orgExternal Web Site Icon may be helpful.
Why Do I Need a Flu Vaccine Every Year?
A flu vaccine is needed every year because flu viruses are constantly changing. It's not unusual for new flu viruses to appear each year. The flu vaccine is formulated each year to keep up with the flu viruses as they change.
Also, multiple studies conducted over different seasons and across vaccine types and influenza virus subtypes have shown that the body's immunity to influenza viruses (acquired either through natural infection or vaccination) declines over time.
Getting vaccinated each year provides the best protection against influenza throughout flu season.
Does flu vaccine work right away?
No. It takes about two weeks after vaccination for antibodies to develop in the body and provide protection against influenza virus infection. In the meantime, you 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.
Can I get seasonal flu even though I got a flu vaccine 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 getting vaccinated, and 2) the similarity or “match” between the virus strains in the vaccine and those circulating in the community. If the viruses in the vaccine and the influenza viruses circulating in the community are closely matched, vaccine effectiveness is higher. If they are not closely matched, vaccine effectiveness can be reduced. However, it's important to remember that even when the viruses are not closely matched, the vaccine can still protect many people and prevent flu-related complications. Such protection is possible because antibodies made in response to the vaccine can provide some protection (called cross-protection) against different, but related strains of influenza viruses.