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August 18, 2021

FDA Authorizes COVID Booster Shots for Some Immunocompromised People

FDA Authorizes COVID Booster Shots for Some Immunocompromised People

As the highly contagious Delta variant causes a surge in new COVID-19 cases, the U.S. Food and Drug Administration (FDA) has authorized booster shots of the Pfizer or Moderna mRNA vaccines for certain people with weakened immune systems. That group includes, “specifically, solid organ transplant recipients or those who are diagnosed with conditions that are considered to have an equivalent level of immunocompromise,” according to the agency’s August 12 statement.

The Centers for Disease Control and Prevention’s (CDC) Advisory Committee on Immunization Practices (ACIP) met on Friday August 13 to weigh available evidence, and unanimously recommended the FDA’s decision, noting that the decision to recieve a third dose should be made by individuals and their doctors. The ACIP's decision was approved by CDC director, Rochelle Walensky, MD, MPH. 

The move comes as new evidence suggests that some immunocompromised people fail to develop a strong initial immune response, and that a third dose of either the Pfizer or Moderna mRNA vaccine is not only safe but could also better protect them over time.

"This official CDC recommendation — which follows FDA’s decision to amend the emergency use authorizations of the vaccines — is an important step in ensuring everyone, including those most vulnerable to COVID-19, can get as much protection as possible from COVID-19 vaccination," said Dr. Walensky in an August 13 statement, noting that immunocompromised people account for 40 to 44 percent of hospitalized breakthrough cases and those with weakened immune systems who are infected more likely to spread the virus to others.

What new research shows
Researchers recruited 120 transplant recipients who had received two doses of the Moderna vaccine. The people involved in the study, who ranged from 63 to 71-years old, had never been diagnosed with COVID-19. They were randomly assigned to receive either a booster or a placebo shot two months after receiving their second dose of the vaccine.

The August 2021 study published in the New England Journal of Medicine found that a third dose of the vaccine dramatically raised protective antibody levels against the coronavirus in the transplant recipients. One month after the third shot, 55 percent of those who got the vaccine developed antibody levels likely to provide significant protection. Meanwhile, the same was true for only 18 percent of those who received the placebo shot.

Other important findings: Counts of protective T-cells—which kick into action and stimulate the production of antibodies and other immune cells that help clear infections—were also higher among the people who received the third dose of the vaccine. The study also showed that receiving a booster dose of the vaccine did not cause organ rejection among any of the participants. Overall, side effects among those who got the third dose were only slightly more common than the placebo group.

“At this juncture, the benefit of third-dose vaccination, at least with the mRNA-1273 vaccine, appears to outweigh the risks,” two editors of the New England Journal concluded in an editorial accompanying the study.

Another June 2021 study by Johns Hopkins published in Annals of Internal Medicine suggests that three doses of the COVID-19 vaccine increase antibody levels among transplant patients. The study included 30 organ transplant recipients who received a third dose of the Johnson & Johnson/Jansen Moderna or Pfizer/BioNTech vaccine. Researchers found that one-third of the participants who had negative antibody levels and all of those who had low positive levels before the booster dose increased their immune response after getting a third shot.

Who is eligible for a booster shot?
Certain people with weak or compromised immune systems are eligible to receive a booster dose of the Pfizer or Moderna COVID-19 vaccine 28 days after their second shot. 

As of September 20, COVID booster shots are available to all Americans who have already received two doses of either the Pfizer or Moderna mRNA vaccines. These people can roll up their sleeves for a third shot, starting eight months after they got their second dose. For example, someone who got their second shot on March 12 can get their booster shot on November 12.  

The booster should be the same vaccine that was given in the previous doses. So, those who got two doses of the Pfizer-BioNTech shot should get another dose of the Pfizer vaccine and those who got two doses of the Moderna shot could get a third dose of this same vaccine.

Why can immunocompromised people get boosters more quickly?
For people with weakened immune systems, the existing COVID-19 vaccines, which are highly effective for healthy adults, may not have the same efficacy rate. So even if they are fully vaccinated, they’re not as protected from the coronavirus.

It’s estimated that about 2.7 percent of U.S. adults are living with weakened immune systems, according to the CDC. Roughly 2.6 percent of children are also immunocompromised. And some 15 million people in these groups won’t develop a strong immune response after being vaccinated against COVID-19, according to Johns Hopkins Medicine.

Having a weakened immune system also puts people at greater risk for severe COVID-19 and death from the infection.

Previously, the hope had been that these people would be protected by herd immunity—when enough people were immune to a disease either through infection or immunization that it’s spread becomes unlikely. But as of August 12, only 50 percent of the total U.S. population is fully vaccinated, and about 30 percent of people who are eligible to be vaccinated still haven’t gotten even one shot, the CDC reports.

Centers for Disease Control and Prevention. "Media Statement from CDC Director Rochelle P. Walensky, MD, MPH, on Signing the Advisory Committee on Immunization Practices’ Recommendation for an Additional Dose of an mRNA COVID-19 Vaccine in Moderately to Severely Immunocompromised People." Aug 13, 2021.
Centers for Disease Control and Prevention. “ACIP Data and Clinical Considerations for Additional Doses in Immunocompromised People.” Jul 22, 2021.
U.S. Food and Drug Administration. “Coronavirus (COVID-19) Update: FDA Authorizes Additional Vaccine Dose for Certain Immunocompromised Individuals.” Aug 12, 2021.
Williams Winfred W., Ingelfinger Julie R.. (2021) Third Time’s a Charm — Covid-19 Vaccine Hope for Solid-Organ Transplant Recipients. N Engl J Med. Aug 11, 2021.
Victoria G. Hall, M.B., B.S., Victor H. Ferreira, Ph.D., Terrance Ku, M.Sc. et al.  “Randomized Trial of a Third Dose of mRNA-1273 Vaccine in Transplant Recipients.” N Engl J Med. Aug 11, 2021.
William A. Werbel, Brian J. Boyarsky, Michael T. Ou, et al. Safety and Immunogenicity of a Third Dose of SARS-CoV-2 Vaccine in Solid Organ Transplant Recipients: A Case Series. Ann Intern Med. [Epub ahead of print 15 June 2021].
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