At-Risk Americans Become Eligible for Fourth COVID Shot This Week

Carolyn Crist

January 10, 2022

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

Some Americans with a weakened immune system who face high risks for severe COVID-19 become eligible this week to receive a fourth dose of a coronavirus vaccine.

The CDC endorsed a third dose of the Pfizer or Moderna vaccines for moderately and severely immunocompromised people on Aug. 13, which is considered part of their first immunization series rather than a booster shot.

In October, the CDC said moderately and severely immunocompromised people could receive a booster shot, or a fourth dose of the vaccine, 6 months after their third dose.

But the CDC last week shortened the timeline to 5 months for a booster shot of the Pfizer or Moderna vaccines. That means immunocompromised people could begin signing up for a fourth shot later this week,  The New York Times reported.   

About 2.7% of U.S. adults, or about 7 million adults, are considered immunocompromised, according to the CDC. They're more likely to contract severe COVID-19, have a higher risk for long COVID, have lower antibody levels after vaccination, and develop serious breakthrough infections. About 40% of hospitalized breakthrough cases are among immunocompromised people.

According to CDC guidance, people are considered to be "moderately or severely immunocompromised" if they have:

  • Active cancer treatment for tumors or cancers of the blood

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

  • Had a stem cell transplant in the last 2 years and are taking medicine to suppress the immune system

  • Advanced or untreated HIV infection

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

  • Active treatment with high-dose corticosteroids or other drugs that suppress the immune response

So far, only moderately and severely immunocompromised Americans are eligible for a fourth shot. Israel has begun offering fourth doses to high-risk groups, including older adults, but the Biden administration hasn't yet said whether the U.S. will follow, the Times reported.

Overall, the focus remains on getting third shots to Americans who are eligible for boosters, Rochelle Walensky, MD, the CDC director, told reporters on Friday. U.S. officials will remain in touch with Israel to follow their data on fourth shots.

"We will be following our own data carefully as well, to see how these boosters are working in terms of waning effectiveness, not just for infection but, importantly, for severe disease," she said.


The New York Times: "Starting later this week, some at-risk Americans become eligible for a 4th shot."

CDC: "ACIP Evidence to Recommendations for Use of an Additional COVID-19 Vaccine Dose in Immunocompromised People."

CDC: "COVID-19 Vaccines for Moderately or Severely Immunocompromised People."


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