An advisory committee to the Centers for Disease Control and Prevention voted Friday to recommend that certain patients with weakened immune systems receive an extra dose of the Pfizer-BioNTech or Moderna vaccine.
The unanimous vote came less than 24 hours after the Food and Drug Administration amended the vaccines' emergency use authorization to include patients with moderate to severe immunosuppression.
CDC Director Dr. Rochelle Walensky signed off on the Advisory Committee on Immunization Practices' decision just hours later, meaning providers can officially start administering the extra dose.
“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,” Walensky said in a statement Friday, adding that the CDC does not recommend booster shots for other groups of people beyond the immunocompromised at this time.
An estimated 2.7 percent of adults in the United States are immunocompromised, according to the CDC. But they make up a significant portion of the fully vaccinated people who are hospitalized with Covid-19, accounting for up to 44 percent.
"I am really grateful that we finally have an expanded EUA, particularly for the immunocompromised so that we can provide more protection for those who may not have responded initially," advisory committee member Lynn Bahta, the clinical expert for the Minnesota Department of Health, said during Friday's meeting.
The extra layer of protection for these particularly vulnerable groups comes at a time when Covid-19 is surging across the U.S., driven by the highly transmissible delta variant.
Since the beginning of July, the country has seen a 700 percent increase in the seven-day average of Covid-19 cases, the CDC said.
Only patients who previously had one of the mRNA vaccines, from either Pfizer or Moderna, would qualify for a third shot. Pfizer’s vaccine is available to people ages 12 and up, and Moderna’s vaccine is available to people ages 18 and up.
The CDC panel suggested that the third dose should match the vaccine previously administered. That is, if a patient first received two doses of Pfizer vaccine, that person's third shot should also come from Pfizer. The same is true for Moderna. If that isn’t possible, however, the CDC committee said either mRNA vaccine would be appropriate. Patients should wait at least 28 days after their second dose to get a third.
Who is considered immunocompromised?
When the FDA announced the expanded authorization for the shots on Thursday, it said the additional doses were for "certain immunocompromised individuals, specifically, solid organ transplant recipients or those who are diagnosed with conditions that are considered to have an equivalent level of immunocompromise.”
Friday, members of the Advisory Committee on Immunization Practices tried to clarify who that included — though they acknowledged that there are no hard and fast definitions and encouraged patients to speak with their doctors about whether an additional dose is needed. The CDC discouraged the use of antibody tests to determine whether a patient needed an additional dose, however, because there are no FDA-approved tests to measure antibody levels after vaccination.
Broadly speaking, the intended recipients of an additional dose includes people who have had organ transplants, cancer patients undergoing treatment that compromises their immune system, as well as people with immunodeficiency syndromes, such as HIV.
It’s not meant to apply to older adults or those with chronic health conditions that could have some potentially smaller impact on the immune system, such as heart disease or diabetes.
Studies have shown that organ transplant recipients in particular "have had the largest deficits in antibody response, ranging from zero to 79 percent," said Dr. Kathleen Dooling, of the CDC's National Center for Immunization & Respiratory Diseases. But, she added, one third to one half of those who had no detectable immune response to the first two mRNA shots ended up responding to a third dose.
According to the United Network for Organ Sharing, 21,061 organ transplants occurred in the first half of 2021, and the group predicts the number will top a record-breaking 40,000 transplants by the end of the year.
In a statement, the National Kidney Foundation said that it applauded the extra dose decision for immunocompromised patients — including kidney transplant recipients — and that it is a "great sigh of relief to kidney patients and the physicians who care for them."
Dr. Helen Keipp Talbot, a member of the Advisory Committee on Immunization Practices and an infectious disease specialist at Vanderbilt University in Nashville, Tennessee, urged caution about assuming that a third dose would provide robust protection. Indeed, more research is needed to better understand the effects of the additional shot.
"I think the reality is, they'll be safer, but still at an incredibly high risk for severe disease and death," Talbot said. That is, immunosuppressed patients will still need to take extra precautions, such as continued masking and physical distancing.
The committee members also acknowledged that restricting who can and cannot get an additional dose may be tricky in the real world. In general, vaccine clinics and pharmacies do not require proof that a patient has an immune disorder and would need an extra shot.
The CDC acknowledged that more than 1.1 million people in the general population had already sought out an additional dose on their own, prior to any authorizations for such doses from federal regulators.
What about Johnson & Johnson?
Immunocompromised patients who received the Johnson & Johnson Covid-19 vaccine have been left out of this latest action.
The CDC committee said there is not yet enough data on immunocompromised patients who got the Johnson & Johnson shot to make any solid recommendation for an extra dose of vaccine in this group.
But the CDC's Dr. Amanda Cohn said Friday that this gap in data will be "short-lived," adding, "we will work as hard as we can to be able to address this adequately and appropriately."
Just under 14 million people in the U.S. have received the Johnson & Johnson vaccine; it is unclear how many of them are considered immunocompromised. Many such patients got their vaccinations early on, before Johnson & Johnson was authorized, and therefore received an mRNA vaccine.
Indeed, many immunocompromised patients were "first in line" to get their Covid-19 vaccines, said Dr. David Cohn, chief medical officer at the Ohio State University Comprehensive Cancer Center.
"They were so excited to protect themselves, and to try to get back to being with their families again," he said.
Now that it is clear that many of those patients have not been well protected by the vaccines, he said the third dose will be a welcome boost in immunity.
"They've done everything that they can do," he said. "They're scared."