This blog was originally posted in 2021. Some information may be out of date. For the latest updates on vaccines, testing, screening, visitor policy and post-COVID support, visit EEHealth.org/coronavirus.

The country is in yet another wave of the COVID-19 pandemic. With cases of COVID-19 surging once again, more contagious variants circulating, and some of us more than six months out from being fully vaccinated, many are wondering about a booster shot to stay protected.

On Aug. 12, the Food and Drug Administration (FDA) amended the emergency use authorizations (EUAs) for the Pfizer-BioNTech and Moderna COVID-19 vaccines, to allow for the use of an additional (third) dose of mRNA COVID-19 vaccine in certain individuals who are moderately to severely immunocompromised.

This third shot isn’t exactly a "booster" shot. Boosters are for people whose immunity wanes over time, but individuals in this high-risk group didn't get enough protection to begin with to mount an adequate immune response. The third vaccine dose is being considered as part of their initial vaccination series.

Who is eligible for a third vaccine dose?

Those currently eligible for a third COVID-19 vaccine dose include certain individuals with weakened immune systems who meet the high-risk requirement, including those who:

• Are receiving 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
• Have moderate or severe primary immunodeficiency (e.g., DiGeorge syndrome, Wiskott-Aldrich syndrome)
• Have an advanced or untreated HIV infection
• Are taking medicine that may suppress immune response

Why immunocompromised individuals?

People with weak immune systems have a reduced ability to fight infections. Immunocompromised individuals are particularly vulnerable to COVID-19 because they are more at risk of serious, prolonged illness, according to the Centers for Disease Control and Prevention (CDC).

Research suggests some immunocompromised people don’t always build the same level of immunity after vaccination the way non-immunocompromised people do. In fact, experts believe immunocompromised people are more likely to get “breakthrough infections” (COVID-19 infection after vaccination) than people with healthy immune systems.

While the mRNA COVID-19 vaccines offer powerful protection for otherwise healthy people, immunocompromised people generally get less benefit from the standard two doses. A third vaccine dose may help boost immunity in these individuals who need extra protection against COVID-19.

According to a recent statement from Pfizer-BioNTech: "The data we’ve seen to date suggest a third dose of our vaccine elicits antibody levels that significantly exceed those seen after the two-dose primary schedule."

When should they get an additional dose?

The CDC recommends that immunocompromised people receive an additional (third) dose of an mRNA COVID-19 vaccine at least four weeks (28 days) after the second dose of either the Pfizer-BioNTech or Moderna COVID-19 vaccine.

Can they mix and match the vaccines?

For people who received either Pfizer-BioNTech or Moderna’s COVID-19 vaccine series, a third dose of the same mRNA vaccine should be used, according to the CDC. If the mRNA vaccine product given for the first two doses is not available or is unknown, either mRNA COVID-19 vaccine may be administered.

What are the side effects of a third dose?

While information continues to be evaluated, so far, reactions reported after the third mRNA dose were similar to the two-dose series, with fatigue and pain at the injection site the most commonly reported side effects. Most symptoms were mild to moderate.

What about those who received the Janssen (J&J) vaccine?

The FDA’s recent EUA amendment and CDC’s recommendation only applies to mRNA COVID-19 vaccines, in which data demonstrate a third dose may result in an improved response in immunocompromised people. There is not enough data at this time to determine whether immune-suppressed individuals who received the one-shot Janssen (J&J) COVID-19 vaccine also have an improved antibody response following an additional dose of the same vaccine.

What about a booster shot for everyone else?

While Pfizer-BioNTech is currently seeking FDA authorization of a third COVID-19 vaccine shot for everyone ages 16 and older — not just those with weak immune systems — booster doses aren’t yet recommended for the general U.S. population, as non-immunocompromised individuals who are fully vaccinated are considered adequately protected at this time.

However, everyone will likely need a booster shot at some point to maintain full protection, just like for the seasonal flu, and health officials are expected to recommend COVID-19 vaccine boosters for all Americans, regardless of age, eight months after their second dose.

If you have questions about your eligibility for an additional COVID-19 vaccine dose, ask your doctor.

Haven’t been vaccinated yet? To date, nearly 170 million people have been fully vaccinated against COVID-19, under the most intense safety monitoring in U.S. history. The evidence is clear and straight-forward. The best way to protect yourself from possible severe illness, long-term health consequences of infection, hospitalization or death is to get vaccinated.

Edward-Elmhurst has COVID-19 vaccine appointments available to ages 12 and older, including those who qualify for a third COVID-19 vaccine dose. It is easy to schedule a vaccine appointment. You do not need a MyChart account. Schedule your COVID-19 vaccine now.

The information in this article may change at any time due to the changing landscape of this pandemic. Read more about COVID-19.