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CDC tackles COVID booster shots for immunocompromised
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CDC tackles COVID booster shots for immunocompromised

  • Sergio Santos/ CC BY 2.0

The three COVID-19 vaccines used in the United States significantly protect most healthy people from the virus, but are less effective for those with certain immune conditions, prompting a top immunization advisory board to discuss whether to recommend a third dose of vaccine for immunocompromised people. 

At a meeting on Thursday of the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices, health experts presented new data on vaccine efficacy, especially related to the 2.7% of American adults who are immunocompromised. They include cancer patients, solid organ or stem cell transplant recipients, and people with HIV.

Not only are people with those underlying immune conditions more likely to get severely ill from COVID-19, but they may also be infected for longer and have breakthrough infections — that is, become infected with the coronavirus after being vaccinated against it.

For example, after 14 days, the Pfizer and Moderna vaccines were just 59% effective at preventing hospitalization among immunocompromised people, compared to the 91% effectiveness rate in those without an immune condition, according to a pre-print study in medRxiv published on July 8.

Emerging data suggests that an additional dose may prompt an immune response when the initial one- or two-dose regimen did not. Among people who had no detectable antibody response at first, 33% to 50% developed an antibody response after an additional dose, according to one slide presented at the meeting.

Some members of the advisory committee felt that progress toward adding a third dose for those who need it has not moved fast enough. 

“The issue is almost running away from us already,” said Dr. Pablo J. Sanchez, pediatrics professor at Ohio State University and a voting member of the committee. 

“These people want to be vaccinated … it seems to me that we should promote that,” Sanchez said, speaking after several people with immune conditions urged faster action during a public-comment period. 

Indeed, another committee member, Dr. Helen Keipp Talbot, said that those desperate for a third shot “many have taken matters into their own hands,” proceeding with additional doses of a vaccine as they see fit.

Talbot, an associate professor of medicine and infectious disease specialist at Vanderbilt University, said she is concerned about patients making this choice unsupervised, which happens because the committee is not allowed to recommend additional doses. 

Plus, she said, the patients taking on their own health care tend to be those more educated and informed. 

“So I worry that some are being left behind,” Talbot said. “Our hands are really tied in the current regulatory situation.”

Before health officials can recommend a third dose of vaccine for immunocompromised people, several review phases need to take place. 

After data is reviewed to assess the safety and implementation questions surrounding a third dose, it would be up to the FDA to adjust its regulations — either altering the current emergency use authorization or adding a biologics license application that would allow the CDC’s advisory committee to make off-label recommendations. Then, the committee or CDC itself could update their recommendations for immunocompromised people. 

We’re still in the first phase, explained Dr. Sara Oliver, a medical officer at the National Center for Immunizations and Respiratory Diseases and the advisory committee’s CDC lead. 

“We will continue to review the data as it becomes available,” she said. “However, while we do that, we need to remember what we can do now.” 

First, people with immune conditions should continue to follow social distancing and masking measures, and avoid crowds. Their close contacts should also be vaccinated, encircling them with another layer of protection. And early treatment with monoclonal antibody therapies may help, too. 

In her presentation to the committee, Oliver noted that some other countries have gone ahead with third-dose recommendations. 

French officials recommend a third dose, four weeks after the second, for patients who are “severely immunocompromised,” and may extend that to a larger group in the future. The United Kingdom announced a proposal earlier this month for an additional dose in immunocompromised people ages 16 and older, to be implemented this fall. And in Israel, people with certain organ or stem cell transplants, blood cancers, autoimmune diseases, or taking certain immunosuppressive medications all qualify for a third dose — while those with breast, lung, or colon cancer do not. 

Groups being considered for a third dose in the U.S. include people with “moderate to severe” immune conditions. 

As for supplying people with a booster shot of a different type than their initial vaccine, some studies in Europe have looked at combining the AstraZeneca and Pfizer vaccines, and “ found immunogenicity to be at least equivalent to a homologous series,” Oliver said, but more information is needed to look at combining the Johnson & Johnson shot with an mRNA-based vaccine. 

No data has been submitted yet to the FDA to support amending the emergency use authorization. 

At Thursday’s meeting, the CDC advisory committee also discussed reports that the J&J shot has been linked to a rare nerve disorder called Guillain-Barré syndrome, which has also been associated with flu shots, and has been seen in some Covid-19 patients as well. 

Presenters and voting members of the committee commented that while people should be informed of all risks associated with vaccines, the benefits — including those of a single-shot, easily transported vaccine like J&J’s — continue to outweigh the risks.

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