Understanding the flu vaccine

Influenza (flu) 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, but millions of people get the flu every year, hundreds of thousands of people are hospitalized and thousands or tens of thousands of people die from flu-related causes every year.

An annual seasonal flu vaccine is the best way to reduce your risk of getting sick with seasonal flu and spreading it to others. Plus, when more people get vaccinated against the flu, less flu can spread through the community.

Flu vaccines cause antibodies to develop in the body starting 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 flu season.  This year all flu vaccines are quadrivalent , meaning they protect against four (4) strains of influenza virus.

Everyone six months of age and older should get a flu vaccine every flu season. Vaccination to prevent influenza is particularly important for people who are at high risk of serious complications from influenza.

Talk to your primary care physician if you have concerns about getting a flu shot. Generally, those who meet any of the below criteria should not get the flu vaccine:  

• Children less than six months of age
• People who are experiencing a moderate to severe illness with a fever at the time of vaccination
• People with life-threatening allergies to any ingredient in the flu vaccine (such as gelatin or antibiotics)*
• People who previously developed the rare neurological disorder Guillain-Barré syndrome after receiving the seasonal flu vaccine

  *People diagnosed with an egg allergy can request an egg-free vaccination

You should get a flu vaccine before flu begins spreading in your community. It takes about two weeks after vaccination for antibodies to develop in the body that protect against flu, so make plans to get vaccinated early in fall, before flu season begins.

CDC recommends that people get a flu vaccine by the end of October, if possible. Getting vaccinated later, however, can still be beneficial and vaccination should continue to be offered throughout the flu season, even into January or later.

Children who need two doses of vaccine to be protected should start the vaccination process sooner, because the two doses must be given at least four weeks apart. Talk to your child’s doctor to see if they need one or two doses of flu vaccine.

A flu vaccine is needed every flu season for two reasons. First, the body’s immune response from vaccination declines over time, so an annual vaccine is needed for optimal protection. Second, because flu viruses are constantly changing, the formulation of the flu vaccine is reviewed each year and sometimes updated to keep up with changing flu viruses.

No. It takes about two weeks after vaccination for antibodies to develop in the body and provide protection against influenza virus infection. That’s why it’s better to get vaccinated early in the fall, before the flu season really gets under way.

Yes. There is still a possibility you could get the flu even if you got vaccinated.

The ability of the flu vaccine to protect a person depends on various factors, including the age and health status of the person being vaccinated, and also the similarity or “match” between the viruses used to make 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 influenza viruses.

Influenza vaccine effectiveness can vary from year to year and among different age and risk groups. For more information, visit the CDC's website regarding vaccine effectiveness or specifics about the current flu season.

According to the CDC, there are many reasons to get a flu vaccine each year. For additional information, please visit their website to learn more.

• Flu vaccination can keep you from getting sick with the flu.
• Flu vaccination has been shown in various studies to reduce the severity of illness in people who get vaccinated but still get sick.
• Flu vaccination can reduce the risk of flu-associated hospitalization, including among children and older adults.
• Flu vaccination is an important preventive tool for people with chronic health conditions.
• Flu vaccination during pregnancy helps protect people from flu during and after pregnancy and helps protect their infants from flu in their first few months of life.
• Getting vaccinated also protects people around you, including those who are more vulnerable to serious flu illness, like babies and young children, older people, and people with certain chronic health conditions.