COVID-19 vaccines for those with weakened immune systems

Some people with weakened immune systems are eligible for a total of 4 doses of a COVID-19 vaccine. This includes three doses in the primary vaccine series and a booster dose.

Having a weakened immune system puts you at higher risk of severe illness from COVID-19 and makes you much more likely to have a breakthrough infection. Studies show that the initial vaccine doses are less effective for people with weakened immune systems, as they don’t always produce enough antibodies to build adequate levels of protection, and that hospitalized breakthrough infections are rare but are also more likely in immunocompromised people.

Those who are immunocompromised are eligible to receive a total of four doses of an mRNA vaccine, such as Pfizer-BioNTech (Comirnaty) and Moderna (Spikevax). This includes three doses in the primary vaccine series and a booster dose. This vaccine series will help to further strengthen your immunity against COVID-19.

Additional vaccine dose eligibility

An additional dose of the COVID-19 vaccine has been authorized by the Food and Drug Administration (FDA) for those individuals ages 5 and older who are moderately to severely immunocompromised. This includes 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

If you are unsure if you or your child are eligible for an additional dose of the COVID-19 vaccine at this time or have concerns about the effectiveness of the vaccine you received, please contact your primary care provider. 

How to schedule your vaccination appointment

We are offering Pfizer-BioNTech (Comirnaty) vaccination appointments through self-scheduling or via MyChart

As a reminder, first and second dose COVID-19 vaccines are currently available to all individuals ages 5 and older. Get more information on the COVID-19 vaccines or schedule a vaccination appointment

How to schedule your additional dose appointment

We are offering additional dose Pfizer-BioNTech (Comirnaty) vaccination appointments through self-scheduling or via MyChart.

As a reminder, first and second dose COVID-19 vaccines are currently available to all individuals ages 5 and older. Get more information on the COVID-19 vaccines or schedule a vaccination appointment.

Frequently asked questions about the additional dose

Who is considered immunocompromised and eligible for an additional dose of the COVID-19 vaccine at this time?

People ages 5 years and older are considered moderately to severely immunocompromised are limited to include those 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 2 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

Those who fall into these categories make up only about 3% of the adult population. Although those with breakthrough COVID-19 infections have been rarely hospitalized, fully vaccinated, immunocompromised people have accounted for a large proportion of those who do end up hospitalized with breakthrough infections. If you are uncertain if you are eligible to receive an additional COVID-19 vaccine dose based on these criteria, please contact your primary care provider.

What if I don’t know if I’m considered immunocompromised, but have health complications that put me more at risk?

If you are unsure if you are eligible for an additional dose of the COVID-19 vaccine at this time or have concerns about the effectiveness of the vaccine you received, please contact your primary care provider.

If I’ve already had a COVID-19 vaccine but am considered immunocompromised, why do I need an additional dose?

Having a weakened immune system puts you at higher risk of severe illness from COVID-19 and makes you much more likely to have a breakthrough infection (breakthrough infections occur when vaccinated individuals contract the disease they’ve been vaccinated against).

Studies show that the initial vaccine doses are not as effective for people with weakened immune systems, as they don’t always produce the same level of antibodies to build adequate levels of protection. Hospitalized breakthrough cases are rare, but are also more likely in immunocompromised people. An additional dose of the vaccine will help to further strengthen your immunity against COVID-19.

In addition to an additional dose, everyone ages 12 years and older who is fully vaccinated against COVID-19 is eligible for a booster shot.

If I’ve already had two doses of a COVID-19 vaccine or one dose of the Johnson & Johnson vaccine, am I considered fully vaccinated?

If you are moderately to severely immunocompromised and have received two doses of the Pfizer-BioNTech (Comirnaty) or Moderna vaccines or one dose of the Johnson & Johnson (Janssen) vaccine, you are no longer considered fully vaccinated and are now recommended to receive the additional dose in the vaccine series to be up to date on your vaccinations.

How do I get an additional dose of the COVID-19 vaccine?

Get more information on receiving an additional dose of the Pfizer-BioNTech Vaccine (Comirnaty) from UI Health Care. Many local pharmacies are also offering the additional dose of the COVID-19 vaccines needed for immunocompromised people. At this time, we are offering only additional dose vaccinations for the Pfizer-BioNTech Vaccine (Comirnaty).

UI Health Care is not yet administering additional doses of the Moderna vaccine, though we have plans to offer this soon. Additional information will be shared when this service is available through UI Health Care.

Many local pharmacies are also offering both the Pfizer-BioNTech (Comirnaty) and Moderna vaccines for this additional dose of the COVID-19 vaccines for immunocompromised people.

If I’m eligible and get an additional dose of the COVID-19 vaccine, will I have enough protection?

The strongest protection comes from getting vaccinated.

Although the additional dose of the COVID-19 vaccine will further strengthen your immunity, it is important to realize that the vaccines are not 100% effective at preventing illness or from contracting (and then spreading) COVID-19. You should also protect yourself and others by wearing a mask, social distancing, avoiding crowds, and washing your hands often. Each of these are important ways to reduce your risk of getting COVID-19, but they become very effective when you combine them.

If you are moderately to severely immunocompromised and do not get an additional dose of the Pfizer-BioNTech (Comirnaty) or Moderna vaccines, you will no longer be considered fully vaccinated.

In addition to an additional dose, everyone ages 12 years and older who is fully vaccinated against COVID-19 is eligible for a booster shot.

Should I get my additional dose of the COVID-19 vaccine if I’m not feeling well?

No. People who are experiencing symptoms associated with COVID-19 should wait to be vaccinated until they have recovered from their illness and have met the criteria for discontinuing isolation if they are found to test positive.

Regardless of your vaccination status or whether or not you are immunocompromised, it is important to get tested if you are experiencing any symptoms of COVID-19 and to stay home if you are sick.

What to do if you feel unwell 

To be safe, you should stay home if you feel unwell. You should also schedule a video visit if you experience any symptoms that are similar to symptoms of COVID-19.

COVID-19 symptoms:

  • A fever in the last 24 hours
  • New or worsening:
    • Sore throat
    • Cough
    • Shortness of breath

I’m not moderately to severely immunocompromised, but I would like to get an additional dose anyway.

Individuals who are age 12 or older and are not immunocompromised should receive a COVID-19 vaccine booster.

Learn more about scheduling a booster

Are immunocompromised children eligible for an additional dose of the COVID-19 vaccine?

The Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) have now authorized an additional dose of the Pfizer-BioNTech COVID-19 vaccine for children ages 5 years and older who are moderately to severely immunocompromised, to be given 28 days after their second dose.

I am moderately to severely immunocompromised and received an additional dose of an mRNA vaccine. Am I eligible to receive a booster?

If you are aged 18 years and older and received an additional dose of the Moderna or Pfizer-BioNTech vaccine you are eligible to receive a COVID-19 booster. For those aged 12 years and older, you are eligible for a Pfizer-BioNTech COVID-19 booster only. Boosters should be administered 3 months after your additional dose. In total, this means that an immunocompromised person aged 12 years and older, may receive a total of 4 doses of a COVID-19 vaccine (3 doses in the initial series, plus 1 booster).

If you received a primary dose of the Johnson & Johnson (Janssen) COVID-19 vaccine, as well as an additional dose for immunocompromised individuals, you may receive a booster dose at least 2 months following your additional dose.

You may be wondering what the difference between a booster dose and an additional dose is. Sometimes people who are moderately to severely immunocompromised do not build enough protection when they first get a vaccination. When this happens, getting an additional dose of the vaccine can help them build more protection against the disease. This is the case for some immunocompromised people and COVID-19 vaccines.

In contrast, a “booster dose” refers to another dose of a vaccine that is given to someone who built enough protection after vaccination, but then that protection decreased over time (this is called waning immunity).

Learn more about the CDC's vaccine recommendations and guidelines.

Last reviewed: 
March 2022

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