Find out if you're eligible for an additional COVID-19 vaccine dose or booster

Last updated October 22, 2021.

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Many people who have already been fully vaccinated against COVID-19 should now receive another dose to stay protected. If you are eligible, getting a booster dose can help protect you, your family, and your community from COVID-19.

All three authorized COVID-19 vaccines are safe, effective, and free. You don’t need an ID, insurance, or an appointment to get vaccinated. Find a COVID-19 vaccine near you.

Booster doses

Who should get a booster dose? 

You should get a booster dose if you:

  • Are 65 years old or older.

  • Live in a long-term care facility.

  • Are 18 to 64 years old and at high risk of severe COVID-19.

  • Are 18 to 64 years old and at high risk because of where you live or work. For example, if you live in a college dorm with lots of other students or you work at a grocery store where you are in contact with many people every day, you may be considered high risk.

  • You received the Johnson & Johnson vaccine for your initial dose.


When should I get a booster dose? 
  • If you received Pfizer or Moderna for your first two doses you should receive your booster dose at least six months after your second dose of vaccine, no matter what vaccine product you receive as a booster.

  • If you received Johnson & Johnson for your initial dose, you should receive your booster dose at least two months after your first dose, no matter what vaccine product you receive as a booster.


Does my booster need to be the same kind of vaccine as my initial doses?
  • No. You can get any authorized vaccine for your booster dose.


Why do I need a booster dose?
  • Booster doses can help give you extra protection from COVID-19. Vaccine effectiveness varies by vaccine product and may decrease over time, and a booster dose can help raise immunity levels. With delta variant circulating and cases of COVID-19 increasing significantly across the United States, a booster will help protect people who are most at risk. Booster doses are common practice in routine childhood vaccines and require multiple doses at specific intervals to be most effective. 


Where can I get a booster dose?
  • You can get a booster dose at any vaccine provider. No ID, insurance, or proof of medical history is required. Booster doses are free. You may self-report having a high risk condition to vaccine providers.

Additional doses for immunocompromised people

Who should get an additional dose?

You should get an additional dose of Pfizer or Moderna if:

  • You have a moderately to severely weakened immune system and received either Pfizer or Moderna vaccines for your first two doses. Your third dose should be the same vaccine product as the first two, but either mRNA vaccine is fine if you can’t get the same kind. If you are 12 to 17 years old, your additional dose must be Pfizer.


When should I get an additional dose?
  • If you are moderately to severely immunocompromised (weakened immune system), you should receive an extra dose of either Pfizer or Moderna at least 28 days after your second dose of mRNA vaccine.


Why do I need an additional dose?


Where can I get another dose?
  • You can get an additional dose at any vaccine provider. No ID, insurance, or proof of medical history is required. Additional doses are free. You may self-report having a high risk condition to vaccine providers.

Use this flowchart to find out if you're eligible for a booster or additional dose. 

Utilice este diagrama de flujo a fin de averiguar si reúne los requisitos para recibir una dosis adicional o de refuerzo.

Frequently asked questions

  • Additional doses are for people with weakened immune systems. Studies show that some people who are immunocompromised don’t build enough protection after receiving two doses of mRNA vaccines. The third dose completes the primary vaccination series and helps protect people with weakened immune systems. 

  • Booster doses are for people who did build enough protection after getting vaccinated at first, but whose protection may have decreased over time.

  • This includes but is not limited to people who have: 

    • Been receiving active cancer treatment for tumors or cancers of the blood. 

    • Received an organ transplant and are taking medicine to suppress the immune system.

    • Received a stem cell transplant within the last two years or are taking medicine to suppress the immune system. 

    • Moderate or severe primary immunodeficiency (such as DiGeorge syndrome, Wiskott-Aldrich syndrome). 

    • Advanced or untreated HIV infection. 

    • Active treatment with high-dose corticosteroids or other drugs that may suppress your immune response.

  • You may talk with a health care provider about your medical condition and whether getting an additional dose makes sense for you, but it’s not required to have a conversation with your provider before getting an additional dose.

  • Coloradans looking to get an additional dose may self-attest that they are eligible. You do not need to provide your medical history to receive an additional dose.

  • People at high risk include people who have underlying medical conditions such as:

    • Cancer.

    • Chronic kidney disease.

    • Chronic lung diseases, including COPD (chronic obstructive pulmonary disease), asthma (moderate-to-severe), interstitial lung disease, cystic fibrosis, and pulmonary hypertension.

    • Dementia or other neurological conditions.

    • Diabetes (type 1 or type 2).

    • Down syndrome.

    • Heart conditions (such as heart failure, coronary artery disease, cardiomyopathies, or hypertension).

    • HIV infection.

    • Immunocompromised state (weakened immune system).

    • Liver disease.

    • Overweight and obesity.

    • Pregnancy.

    • Sickle cell disease or thalassemia.

    • Smokers, current or former.

    • Solid organ or blood stem cell transplant.

    • Stroke or cerebrovascular disease, which affects blood flow to the brain.

    • Substance use disorders.

  • Some people may also be at high risk for getting COVID-19 because of where they live or work. Things you can consider when weighing risk include: 

    • Do you live or work with unvaccinated people or children not yet eligible for the vaccine? 

    • Do you work with others who are at high risk? 

    • Do you often interact in-person with members of the public at work? 

    • Do you live in a congregate setting with many other people?

  • Coloradans looking to get a booster dose may self-attest that they are eligible. You do not need to provide your medical history or employment status to receive a booster dose.

  • Yes. Right now, the definition of “fully vaccinated” is still the same. You are considered fully vaccinated if more than two weeks have passed since your second dose of Pfizer or Moderna, or your single dose of J&J vaccine.

  • No. You do not need to be a full-time resident of Colorado, or of a particular Colorado county, to be vaccinated.

  • Vaccines must be proven to be safe and effective before they are given to people. The COVID-19 vaccines are no different. These vaccines are being proven safe every day, as hundreds of thousands of Coloradans – doctors, nurses, seniors, and others – have already taken them. Nationwide, many millions of people have also received the vaccine.

  • The FDA requires that vaccines undergo a rigorous scientific process, including three phases of clinical trials, before they authorize or approve the vaccine. The COVID-19 vaccines are subject to the same safety standards as other vaccine trials.

  • You may experience mild to moderate side effects after receiving the vaccine. Side effects are about the same for the first, second, and third doses of the vaccines. Side effects typically go away on their own after a few days. The most commonly reported side effects are: 

    • Pain, swelling, and redness at the injection site.

    • Pain, tenderness, and swelling of the lymph nodes in the same arm of the injection.

    • Fatigue.

    • Headache.

    • Muscle pain.

    • Chills.

    • Joint pain.

    • Nausea/vomiting.

    • Fever.

  • Different people may experience different side effects, even if they receive the same vaccine. 

  • The process of building immunity can cause symptoms. These symptoms are normal and show that your body’s immune system is responding to a vaccine. Other routine vaccines, like the flu vaccine, have similar side effects.

  • If you experience discomfort after the first dose of the Pfizer or Moderna vaccine, it is very important that you still receive the second dose a few weeks later for full protection.

  • For in-depth information about the side effects of the vaccines, see the CDC’s report on Pfizer vaccine, Moderna vaccine, and Janssen (Johnson & Johnson) vaccine. 

For more information on the COVID-19 vaccine, please call:

1-877-CO VAX CO (1-877-268-2926)
Available Monday through Friday, 8 a.m. to 8 p.m.;
Saturday and Sunday, 9 a.m. to 6 p.m. MT.
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