Complete Guide to Flu Vaccines

According to the Centers for Disease Control, flu or influenza viruses have caused between 9.4 and 41 million illnesses in the U.S. each year since 2010. The National Institutes of Health reports that they cause 31.4 million outpatient visits and more than 200,000 hospitalizations each year.

The best weapon we have against the flu is to get a flu vaccine every year before flu season begins. The CDC recommends that everyone over 6 months old get vaccinated every year.

Research on the first flu vaccines began during the 1918 flu pandemic, but it was not until 1945 that the first flu vaccine was authorized for widespread use in the US.

Path to better health

Flu vaccines protect against the major viruses that researchers predict will be most common during that year’s flu season. While most are administered into the arm with a needle, nasal spray flu vaccines are also available.

Most flu vaccines contain a form of the flu virus that can be live or dead (but weakened). They may also contain egg or animal protein, preservatives (to prevent spoilage), stabilizers (to prevent them from losing strength over time), and sometimes very low amounts of antibiotics (to avoid contamination during production).

Some different types of flu vaccines available include:

  • Flu vaccines in standard doses. These are made by growing the flu virus in an egg. They are available in different brands and are most often administered with a needle.
  • Cell-based flu vaccines. These are made by growing the virus in a cell culture. This means that the cells are grown in a laboratory environment. This vaccine does not contain any eggs.
  • Recombinant flu vaccines. This means that the vaccine is made without using viruses or eggs. It has three times more antigen (the part that helps the body develop protection against the virus) and can help create a stronger immune response in your body.
  • High-Dose Egg-Based Flu Vaccines. These are for use by people 65 years and older. They have four times more antigen than a regular flu vaccine.
  • Egg-Adjuvanted Flu Vaccine. An adjuvant is an ingredient that helps create a stronger immune response in your body. These are also for people over 65 years old.

You should ask your doctor what type of flu vaccine is best for you.

Things to consider

Everyone over 6 months old should get a flu vaccine each flu season. It is recommended to get the flu vaccine along with another vaccine at the same visit if you are eligible and if the timing of each vaccine is appropriate. Vaccines can prevent you from getting sick and reduce your chance of serious illness if you get sick. It can also reduce the risk of having to be hospitalized because of the flu.

The flu vaccine has some side effects, but they are usually very mild. The most common side effects are:

  • Pain, redness, and/or swelling where the injection was given
  • Headache
  • Fever
  • Nausea
  • Muscle pain and fatigue.

These side effects usually go away on their own after a few days. If not, talk to your doctor.

People who have severe and life-threatening allergies to ingredients in flu vaccines should not receive it. This could include gelatin or antibiotics. If you have had a strong allergic reaction to a flu vaccine in the past, talk to your doctor before getting another vaccine.

For pregnant women, the flu vaccine can help protect you and your baby and may prevent you from getting sick during the first few months after birth. Flu vaccines can also reduce the risk of severe and life-threatening flu in children by 75%.

Getting a flu shot can also protect people around you who are more likely to get sick, such as babies, young children, and older people with existing medical conditions. If you have an existing health problem, talk to your doctor before getting a flu shot.

Questions to ask your doctor

  • Do I need to get a flu vaccine?
  • Which flu vaccine is right for me?
  • How old do my children have to be before they can get the flu vaccine?
  • Are there any risks associated with the flu vaccine?
  • What are the side effects of receiving the flu vaccine?
  • Why do I need to get a flu shot every year?
  • When should I get a flu shot?


Centers for Disease Control: Seasonal Flu Vaccines

Influenza disease burden | Centers for Disease Control and Prevention Find Flu Vaccines

This content was developed independently by the AAFP and was made possible with financial support from AstraZeneca.

Copyright © American Academy of Family Physicians

This information provides a general overview and may not apply to everyone. Talk to your primary care doctor to find out if this information applies to you and for more information on this topic.

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