Commonly Asked Questions: 3rd-Dose COVID-19 Vaccinations

Currently, only those with an underlying condition that weakens their immune system are approved to get a 3rd dose of an mRNA vaccine (Pfizer or Moderna). 

These patients typically don't have as strong a response to the vaccine. This leaves them less protected than those with healthier immune systems. Studies of the vaccine show protection increases for these patients with a 3rd dose.

We answer common questions below. If you have other questions, we encourage you to talk to your doctor or other health care provider.

While the Biden administration has announced intention to begin offering 3rd doses to other patients in September, those details aren't yet worked out. We'll share information on this site when the process and timeline are clear.

  • No, a third dose is not currently recommended due to age alone. The definition of moderately or severely immunocompromised, for the purpose of additional vaccine doses, is outlined below.

  • Individuals who have already received 2 doses of a mRNA COVID-19 vaccine with the second dose at least 28 days ago AND who have moderate or severe immunocompromise.

    If you have questions about whether you are eligible based on your health condition, please talk to your doctor.

    The CDC’s Advisory Committee on Immunization Practices (ACIP) and VUMC define moderately or severely immunocompromised patients as patients who have any of these conditions:

    • Under active treatment for solid tumor or hematologic malignancy
    • Solid organ transplant patient on immunosuppressive therapy
    • Hematopoietic stem cell transplant in last 2 years or otherwise on immunosuppression therapy after stem cell transplant
    • Receipt of CART-cell therapy in last 2 years
    • Primary immunodeficiency syndrome (Common Variable Immune Deficiency, DiGeorge Syndrome, Wiskott-Aldrich syndrome)
    • Advanced (CD4<200) or untreated HIV infection
    • Active treatment in last month with one of the following immunosuppressing drugs:
      • High dose corticosteroids (≥20mg prednisone or equivalent per day for ≥14 days)
      • Alkylating agents (ex: cyclophosphamide, temozolomide, chlorambucil, carboplatin, cisplatin)
      • Antimetabolites (ex: methotrexate, hydroxyurea, gemcitabine, fludarabine)
      • TNF alpha inhibitors (ex: adalimumab, etanercept, infliximab)
      • Other biologic agents that are immunosuppressive or immunomodulatory (e.g., rituximab, anakinra, golimumab, natalizumab)

    Additionally, chronic medical conditions such as End Stage Renal Disease may be associated with varying degrees of immune deficit.


  • Pfizer is approved for age 12 years and older and Moderna for 18 years and older.

  • The FDA authorized immunocompromised individuals to receive a 3rd dose at least 28 days following the 2nd dose of the same vaccine. If you are immunocompromised and received your second dose more than 28 days ago, you can get a 3rd dose.

  • You should get the same brand of mRNA vaccine (Pfizer or Moderna) for the 3rd dose that you received for the 1st and 2nd doses.

    However, if the same brand is not available, you may use either mRNA vaccine brand (Pfizer or Moderna) available.

  • Not currently. No data support the use of an additional vaccine dose after a primary Johnson & Johnson vaccine in immunocompromised people. The FDA and CDC are working to provide guidance on this issue.

  • No. An antibody test is not necessary. It would not change the decision to give you an additional dose.

  • Not unless you meet the CDC and VUMC criteria for moderate or severe immunocompromise. It is important to note that the absence of antibodies on antibody tests does not necessarily indicate a lack of protection against the COVID-19 virus.

  • Based on preliminary studies, the side effects appear to be like the initial vaccine reactions. They may be more pronounced.

    These include pain, redness and swelling at the injection site, as well as tiredness, headache, muscle pain, chills, fever, and nausea.

    So far, there have been no serious side effects to additional dosing, but we will monitor patients closely.

  • Yes, please let your care team know if you get an additional dose of the vaccine, so we have an accurate report of your vaccination status in your health records.

  • If you are eligible, you can get your 3rd shot in these ways:

    • At an upcoming visit with us, ask your provider during your visit
    • Go to and make an appointment.
    • Go to any place that giving COVID-19 vaccines, such as your local health department or a retail pharmacy.
  • No. All close contacts of immunocompromised persons should get vaccinated with the initial vaccine series (2 doses of mRNA vaccine) to prevent the spread of the COVID-19 virus to these vulnerable persons.

    A 3rd dose for such close contacts is not recommended.

  • Because you are immunocompromised, even with a 3rd dose, you may still be at risk of contracting COVID-19 infection.

    You should still take the other recommended precautions from the CDC (such as masking when in public indoor spaces) until the presence of COVID-19 and its spread in our community has gone down a lot.