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 recent flu seasons, between 80% and 90% of flu related deaths have occurred in people 65 years and older. "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 at higher levels in the U.S. 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 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 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 the influenza viruses that research indicates will be most common during the upcoming season. Traditional flu vaccines (called "trivalent" vaccines) are made to protect against three flu viruses; an influenza A (H1N1) virus, an influenza A (H3N2) virus, and an influenza B virus. There are also flu vaccines made to protect against four flu viruses (called "quadrivalent" vaccines). These vaccines protect against the same viruses as the trivalent vaccine and an additional B virus.
What kinds of flu vaccines are available?
There are several flu vaccine options for the 2015-2016 flu season.
Traditional flu vaccines made to protect against three different flu viruses (called "trivalent" vaccines) are available. In addition, flu vaccines made to protect against four different flu viruses (called "quadrivalent" vaccines) also are available.
Trivalent flu vaccine protects against two influenza A viruses (an H1N1 and an H3N2) and an influenza B virus. The following trivalent flu vaccines are available:
- Standard-dose trivalent shots that are manufactured using virus grown in eggs. There are several different flu shots of this type available, and they are approved for people of different ages. Some are approved for use in people as young as 6 months of age. Most flu shots are given with a needle. One standard dose trivalent shot also can be given with a jet injector, for persons aged 18 through 64 years.
- A high-dose trivalent shot, approved for people 65 and older.
- A trivalent shot containing virus grown in cell culture, which is approved for people 18 and older.
- A recombinant trivalent shot that is egg-free, approved for people 18 years and older.
The quadrivalent flu vaccine protects against two influenza A viruses and two influenza B viruses. The following quadrivalent flu vaccines are available:
- A quadrivalent flu shot that is manufactured using virus grown in eggs. There are several different flu shots of this type available, and they are approved for people of different ages. Some are approved for use in people as young as 6 months of age.
- An intradermal quadrivalent shot, which is injected into the skin instead of the muscle and uses a much smaller needle than the regular flu shot. It is approved for people 18 through 64 years of age.
- A quadrivalent nasal spray vaccine, approved for people 2 through 49 years of age.
Are any of the available flu vaccines recommended over others?
For the 2015-2016 flu season, the Advisory Committee on Immunization Practices (ACIP) recommends annual influenza vaccination for everyone 6 months and older with either live attenuated influenza vaccine (LAIV) or inactivated influenza vaccine (IIV) with no preference expressed when either vaccine is available.
There are many vaccine options to choose from, but the most important thing is for all people 6 months and older to get a flu vaccine every year. If you have questions about which vaccine is best for you, talk to your doctor or other health care professional.
Who should get vaccinated this season?
Everyone 6 months of age and older should get a flu vaccine every season. This recommendation has been in place since February 24, 2010 when CDC's Advisory Committee on Immunization Practices (ACIP) voted for "universal" flu vaccination in the United States to expand protection against the flu to more people.
Vaccination to prevent influenza is particularly important for people who are at high risk of serious complications from influenza. See People at High Risk of Developing Flu-Related Complications for a full list of age and health factors that confer increased risk.
For more information about the flu, please visit CDC.gov