The Centers for Disease Control and Prevention on Friday recommended those with compromised immune systems get a third dose of a COVID-19 vaccine, paving the way for millions of people with certain medical conditions to receive an additional shot of either the Pfizer or Moderna vaccines.
The CDC recommendation follows the decision late Thursday by the Food and Drug Administration to broaden its emergency use authorization to include a third shot of the vaccines made by Pfizer-BioNTech and Moderna for some immune-compromised people.
CDC chief Dr. Rochelle Walensky said the recommendations are “an important step in ensuring everyone, including those most vulnerable to COVID-19, can get as much protection as possible from COVID-19 vaccination.”
So, who exactly qualifies for the additional shot?
The CDC recommendation applies to people who are moderately to severely immunocompromised, such as cancer patients, those who have received organ or bone marrow transplants, people who have an immune deficiency, and people with advanced or untreated HIV.
It also applies to people who are taking immune-suppressive medications for underlying autoimmune conditions such as multiple sclerosis, colitis, rheumatoid arthritis, lupus, and psoriasis. The guidance also includes people with chronic renal disease and people who don’t have a spleen.
According to the CDC, there are about 7 million immunocompromised adults in the country, representing less than 2.7 percent of American adults.
Those with qualifying conditions will not need a doctor’s permission or a prescription to receive the shot, CDC officials said Friday, but need to attest that they are eligible.
The change to the emergency use authorization only applies to the two-dose regimens developed by Moderna and Pfizer-BioNTech, not the one-dose Johnson & Johnson vaccine, because of “insufficient data,” the CDC said. Eligible patients can get a third dose of the Pfizer and Moderna vaccines at least 28 days after their second dose. They should try to receive the same vaccine that they initially received, the CDC stated, but a different dose is permitted.
US health officials acknowledged that some 1 million people have already managed to secure additional shots on their own, before they were authorized. That’s one of the several indications that the third shot will be popular.
Dr. Helen Boucher, an infectious diseases physician at Tufts Medical Center and interim dean at the Tufts University School of Medicine, said phones at the hospital are already “ringing off the hook” with patients inquiring about a third dose.
Boucher noted that clinics administering vaccines in Massachusetts follow guidance from the state’s Department of Public Health, and she anticipated they would hear from the state at some point next week.
“They usually follow the CDC, but we need to wait for them to tell us what they’re going to recommend before we can start doing it, start vaccinating,” Boucher said.
The Massachusetts Department of Public Health did not return a request for comment.
But already one major provider of vaccines, CVS Pharmacy, said it would begin providing an additional shot to eligible people immediately. Patients can sign up for appointments on the company’s website beginning Saturday morning and will be “required to attest to their eligibility during the scheduling process and at the time of receiving their vaccination,” said spokeswoman Tara Burke.
Dr. Paul Sax, clinical director of infectious diseases at Brigham and Women’s Hospital, said those who are being treated for cancers such as leukemia, lymphoma, and multiple myeloma have been found to be at particularly high risk for getting severe COVID-19.
Allowing for those with compromised immune systems to receive a third shot makes sense when considering the rise of the Delta variant and data that show that group is not as protected after vaccination, Sax said.
“There are now quite a few studies that show that giving an additional dose does boost their immune response, so I think it makes sense as long as we have sufficient supply and it’s not taking vaccines away from people who weren’t vaccinated at all,” Sax said. “And that’s not the case right now.”
Sax said he hopes the CDC would follow suit with Johnson & Johnson vaccine, which he believes is less effective than the other two and “that lower effectiveness would apply to immunocompromised people.” Patients should speak with their doctors about the possibility of receiving an additional dose, Sax added.
“My medical advice would be that people who’ve had the J&J vaccine should get a booster,” Sax said.
And, Boucher, the Tufts physician, further cautioned that people with compromised immune systems may still be at risk for COVID-19, even with the additional vaccine dose. They should continue to take precautions, including wearing masks, spending time outdoors as much as possible, and avoiding crowded, indoor, poorly ventilated places that are higher risk for spreading COVID-19.
The government’s recommendation is based on laboratory data that show a third dose is associated with an improved antibody response to the vaccine, she said. While encouraging, it is not definitive that a third dose leads to better clinical protection, Boucher said, such as less illness as a result of the virus.
“It is likely that these patients will still have less protection than a non-immunocompromised person, and it may be that the benefit is not as great as we would hope,” Boucher said.
The CDC said that immunocompromised people are more likely to have severe COVID-19 and breakthrough infections. The agency on Friday cited a study that found that 40 to 44 percent of hospitalized breakthrough cases are immunocompromised people.
The CDC’s recommendation highlights the need for eligible people to get vaccinated, Boucher added, because it will also provide protection for immunocompromised people.
“Surrounding immunocompromised people with fully protected vaccinated people is the best protection you can give them,” Boucher said.
The United States is the latest country to begin offering third doses to those with weaker immune systems. France has offered the extra dose to immunocompromised people since April, and Germany will start to do so in September. Israel has started administering the extra shots to immunocompromised people, as well as people over 60.
The CDC’s recommendation comes as the highly transmissible Delta variant is increasing COVID-19 cases, deaths, and hospitalizations, largely among areas that are less vaccinated.
Massachusetts on Friday reported 1,182 new confirmed COVID-19 cases and 11 new confirmed deaths. As of Aug. 7, 106 people who have been fully vaccinated against COVID-19 have died from the virus in Massachusetts, representing 0.002 percent of the 4,321,931 fully vaccinated people, according to data on breakthrough infections the state released this week.
There have also been 9,969 breakthrough COVID-19 infections, representing about 0.23 percent of the total, and 445 hospitalizations among fully vaccinated people, or 0.01 percent.
Information from Globe news services was used in this report. Globe Correspondent Nick Stoico contributed to this story.