Vaccine Reactions
Vaccine Reactions

Vaccines are prescription medications. Like any medication, they can cause reactions in some people.

What kind of reactions can occur after I get a vaccine?

Reactions from vaccines can range from mild symptoms, such as swelling and tenderness at the injection site to more serious reactions, such as difficulty breathing. We continue to learn about these reactions as the field of immunology evolves.

Sometimes the terms "side effect" and "adverse event" are used interchangeably; however, there is a difference between these two terms.

What is a side effect?

Side effects are mild. They go away on their own or with over-the-counter pain and fever reducers.

Some people may have:

  • itching, burning, redness or swelling at the site where the vaccine was given
  • muscle aches, headache, fatigue, fever, body and/or joint aches, etc.

Side effects usually last fewer than 7 days.

What is an adverse event?

Vaccine adverse events are defined as new onset symptoms or illness that:

  • appear within the first few days or weeks after receiving one or more vaccines;
  • have no apparent explanation;
  • impact quality of life, such as:
    • loss of work time or ability to perform usual activities.
    • hospitalization/quarters or emergency/unscheduled medical visits
  • last for more than a few days and/or do not respond to over-the-counter medication.

To see examples of Reportable Adverse Events click here

What should I do if I have a reaction to a vaccine?

Generally, for mild and expected side effects, taking an over-the-counter pain reliever/fever reducer is sufficient. If these problems last for more than a 7 days or get worse, contact your healthcare provider.

For more serious vaccine reactions, contact your healthcare provider.

If it is an emergency, such as chest pain or shortness of breath, go to the closest hospital.

You or your provider may also contact the Military Vaccine Agency - Vaccine Healthcare Centers Network for assistance with documentation, management, and reporting of the vaccine reaction and for future vaccine recommendations and exemptions.

For information, visit our Vaccine Adverse Event Reporting System (VAERS) page.