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  • The FDA authorized the emergency use of a third dose of mRNA vaccines for certain people with severely weakened immune systems.
  • It’s unclear whether immunocompromised people who received the J&J vaccine would be able to get a second dose of an mRNA vaccine.
  • Vaccination also indirectly protects people who are immunocompromised by reducing the spread of the virus in the community.

People with severely weakened immune systems can now get a third dose of an mRNA COVID-19 vaccine.

The Food and Drug Administration (FDA) on Thursday authorized the emergency use of a third dose of the Pfizer-BioNTech or Moderna-NIAID COVID-19 vaccines for certain people with severely weakened immune systems.

This follows growing evidence that some immunocompromised people may not generate a robust immune response from the normal two-dose regimen of these mRNA vaccines.

The agency updated the emergency use authorization (EUA) for both vaccines, along with the fact sheets for healthcare professionals and recipients and caregivers.

This allows “solid organ transplant recipients or those who are diagnosed with conditions that are considered to have an equivalent level of immunocompromise” to receive a third dose of an mRNA vaccine at least 28 days following their second dose.

The update applies to people 12 years and older for Pfizer-BioNTech and 18 years and older for Moderna-NIAID — the age range for which the vaccines are currently authorized.

The change does not apply to the one-dose Johnson & Johnson vaccine, which has been used far less in the United States than the mRNA vaccines.

It’s unclear whether immunocompromised people who received the J&J vaccine would be able to get a second dose of an mRNA vaccine.

“The country has entered yet another wave of the COVID-19 pandemic, and the FDA is especially cognizant that immunocompromised people are particularly at risk for severe disease,” acting FDA Commissioner Dr. Janet Woodcock said in a statement released on Thursday.

“After a thorough review of the available data, the FDA determined that this small, vulnerable group may benefit from a third dose of the Pfizer-BioNTech or Moderna vaccines,” she said.

The vaccine advisory panel of the Centers for Disease Control and Prevention met today and recommended that immunocompromised people get a third dose of either the Pfizer-BioNTech or Moderna-NIAID vaccine.

The CDC is expected to endorse the committee’s decision later on Friday, reports NPR. The agency will also clarify which immunosuppressive conditions are severe enough to warrant a third dose.

Technically not considered a “booster” dose

Dr. David Cohn, an oncologist and chief medical officer at The Ohio State University Comprehensive Cancer Center, pointed out that this additional dose is not considered a “booster.”

Boosters are vaccine doses given to people who generated a strong immune response from the original regimen, but had a waning of that immunity over time. 

Many people who are immunocompromised don’t generate a strong immune response to two doses of an mRNA vaccine.

“This is a third vaccination that, in this population, allows them to get above the threshold that they have never experienced,” said Cohn. “This would allow them to be protected against severe disease or dying of COVID-19. And that’s why it’s really important.”

Although some people with weakened immune systems have less of a response to two doses, Cohn said this is not a failure of the vaccines.

“In the majority of the population, these are very effective vaccines, and people should be encouraged to do what they can to protect themselves and protect society by being vaccinated,” he said.

Vaccination also indirectly protects people who are immunocompromised by reducing the spread of the virus in the community.

An estimated 2.7 percent of U.S. adults are immunocompromised. This is a wide category that includes cancer patients, organ transplant recipients, and people with HIV/AIDS.

Certain medications can also suppress the immune system, like oral corticosteroids, transplant anti-rejection drugs, and drugs used to treat rheumatoid arthritis.

Third dose may increase immune response

Several studies have looked at the immune response of immunocompromised people after COVID-19 vaccination.

One study in JAMA found that 46 percent of organ-transplant recipients had no measurable antibody response after one or two doses of an mRNA vaccine.

But 39 percent of people who had no measurable antibody response after the first dose saw improvement after the second dose.

Dr. Jiha Lee, a clinical assistant professor of rheumatology and internal medicine at the University of Michigan Medical School, said results like these suggest that a third dose might have a similar effect.

People are hoping that there will potentially be a “dose-dependent” effect, she said, with a third dose leading to a better immune response for some immunocompromised people.

Some research supports the use of an additional dose for people with weakened immune systems.

A study from The New England Journal of Medicine found that organ-transplant recipients who received a third dose of the Moderna-NIAID vaccine saw greater improvements in antibody levels, compared with people who received an inactive placebo.

But not every person benefitted.

Of the people who received a third dose, 60 percent developed neutralizing antibodies above a certain threshold. Only 25 percent in the placebo group saw this large of an increase.

Because some immunocompromised people may not see a strong immune response even after a third dose, Cohn recommends that those who are at highest risk of COVID-19 “be vaccinated and act unvaccinated.”

This means continuing to wear a face mask in public settings, limiting their exposure to others, and encouraging direct contacts to get vaccinated — along with following the FDA’s and CDC’s guidelines for vaccination.

“Between all of those things, then you’d be in a good position to be maximally protected,” said Cohn.

Who is eligible for a third COVID-19 vaccine dose?

The CDC posted a list on its website of immunosuppressive conditions severe enough to warrant a third dose.

They include a variety of health conditions including people who are undergoing cancer treatment or who are on immunosuppressing drugs. People with these conditions are urged to talk to their health care provider about whether or not they should get another COVID-19 dose.

The CDC listed the conditions as:

  • Undergoing active cancer treatment for tumors or cancers of the blood.
  • Having had an organ transplant and are taking medicine to suppress the immune system.
  • Having had 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

No boosters recommended yet for most in U.S.

Most studies have looked at additional doses for organ transplant recipients, but Cohn thinks other groups of immunocompromised people might also benefit.

“If you have the ability to generate some immune response to a vaccination, it doesn’t matter why your immune system is not working effectively,” he said. “You still would benefit from being vaccinated a third time.”

Lee said additional research is needed on specific groups of immunocompromised people, because they may have distinct side effects from the vaccine.

“Studies are showing that anywhere from five to 10 percent of our [rheumatoid arthritis] patients are experiencing a flare after [COVID-19] vaccination,” she said. “So if they have a better immune response after the third dose, does that also mean that they will have a higher risk of having a flare?”

“This is tied into safety and efficacy issues around the vaccine, and vaccine hesitancy for a lot of our patients,” she added.

Currently, additional doses of COVID-19 vaccines are not recommended for any people in the United States other than those with weakened immune systems.

“As we’ve previously stated, other individuals who are fully vaccinated are adequately protected and do not need an additional dose of COVID-19 vaccine at this time,” said Woodcock in the release. “The FDA is actively engaged in a science-based, rigorous process with our federal partners to consider whether an additional dose may be needed in the future.”

The FDA is expected to make a decision on full approval of the Pfizer-BioNTech vaccine, and lay out a national strategy on COVID-19 booster doses for most people living in the United States by early September.

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