The Centers for Disease Control and Prevention’s vaccine advisers agreed unanimously to recommend an extra dose of the COVID-19 vaccine for people with weakened immune systems but acknowledged that the details pose tricky questions.
The Advisory Committee on Immunization Practices, or ACIP, on Friday voted 11-0 to recommend a third mRNA dose for a small subset of people who fail to mount an immune response with the standard two doses and are highly vulnerable to COVID-19.
The decision came hours after the Food and Drug Administration amended its emergency authorizations of the Moderna and Pfizer vaccines to make these patients eligible. The third dose is meant to help a few million people with organ transplants who take anti-rejection medications that suppress the immune system, or people with similarly compromised immune systems. They make up less than 2.7 percent of the population.
But ensuring that only people who meet that narrow category get another shot will be nearly impossible.
Some members of ACIP expressed concern that relying on an honor system would open the door to other people with chronic conditions that can impact the immune system, such as diabetes and heart disease. That could create greater demand for vaccine doses considered precious amid a global shortage.
ACIP member Camille Nelson Kotton, while supportive of the booster, said she was concerned about the “nuts and bolts” of the rollout.
“I’m sort of suspicious that many people who are more than a month out from their last vaccine will be going out this weekend to get themselves another dose,” said Kotton, who is the clinical director of immunocompromised care in the infectious diseases division of Massachusetts General Hospital.
Other ACIP members said they had already received requests from patients with a normal immune response to write them a letter recommending a third shot.
Pharmacists are expected to ask people seeking a third dose whether they are moderately or severely immunocompromised but are not expected to require any documentation.
“It will be a patient’s attestation, and there will be no requirement for proof or prescription or a recommendation from an individual’s health care provider,” said CDC official Amanda Cohn.
Cohn said the CDC’s clinical guidance would be updated Friday and that educational materials were being prepared for doctors and patients. She added that CDC was working with state and city public health agencies and pharmacy groups.
Other ACIP members stressed that a hands-off approach is important to ensure it’s not only the best-resourced patients with regular access to good medical care who obtain the extra shot. Requiring a doctor’s note could deter people without health insurance or a primary care physician.
The CDC also said it’s important to give health care providers flexibility when making choices for individual patients. But the CDC is not recommending use of serologic tests or cellular immune testing to guide whether someone needs another dose or not.
“Due to variability in commercial tests, there are actually no tests that are FDA approved for testing antibody levels post-vaccination, so interpretation of such would be very difficult and not particularly useful,” said CDC official Kathleen Dooling.
Pablo Sanchez, an ACIP member and clinician at Nationwide Children’s Hospital in Ohio, pushed back on that, pointing out that many of the studies that CDC cited earlier that day relied on the same sort of tests.
The committee also considered whether to tailor the recommendation further to include only immunocompromised adults, not immunocompromised adolescents over 12 years old who are eligible for the Pfizer vaccine. But ACIP determined that highly vulnerable adolescents may not be at a heightened risk for the most worrisome side effect in young people: myocarditis, a kind of heart inflammation.
The benefits of shielding children with common pediatric cancers like leukemia and lymphoma from COVID-19 outweigh the more remote risks of a side effect, the committee determined.
“If it were my child that were immunocompromised, I would definitely try to get them an extra dose,” said Kotton.
The CDC’s vaccine safety surveillance system, V-Safe, will be updated over the weekend to detect any safety signals associated with a third dose, according to CDC official Karen Broder.
Cohn also said the agency is exploring other ways to monitor safety.
One outstanding question is how to protect immunocompromised patients who received a single-shot Johnson & Johnson vaccine. While Johnson & Johnson is currently conducting a two-dose clinical trial, CDC and FDA officials said they didn’t yet have the data to recommend a second shot.
At the same time, the CDC expects that most immunocompromised people would have received mRNA vaccines. Just 12 million people received the Johnson & Johnson shot, and immunocompromised people were among the first in line for a Moderna or Pfizer shot after they were authorized by FDA last winter.
But top FDA vaccine reviewer Peter Marks said the agency is also working with Johnson & Johnson on assessing a third shot option for people receiving that vaccine.