COVID-19 booster vaccine: FDA approves 3rd shot for immunocompromised

The U.S. Food and Drug Administration has authorized an additional COVID-19 booster vaccine for people who have compromised immune systems as the highly contagious delta variant continues to fuel a resurgence of U.S. infections.

The agency announced the approval on Thursday evening, saying boosters would be a third dose of the Pfizer and Moderna COVID-19 vaccines for people who are immunocompromised at least 28 days after getting their second shot. The FDA made no mention of such patients who received the single-dose Johnson & Johnson vaccine.

"Today’s action allows doctors to boost immunity in certain immunocompromised individuals who need extra protection from COVID-19," Dr. Janet Woodcock, the FDA's acting commissioner, said in a statement.

Immunocompromised people can include organ transplant recipients, cancer patients, or people with other conditions. The U.S. Centers for Disease Control and Prevention has previously identified people with severely weakened immune systems as being at higher risk for getting severely ill from COVID-19, more likely leading to hospitalization or death. 

Importantly, the FDA’s decision only applies to this high-risk group. Fully vaccinated people who do not have weakened immune systems do not need booster shots "at this moment," Dr. Anthony Fauci said earlier Thursday — an assertion echoed by the CDC. Data is currently being collected for other vaccinated groups, such as the elderly, to determine if or when their protection falls below a critical level.

The CDC is expected to formally recommend the extra shots for certain immune-compromised groups after a meeting Friday of its outside advisers.

The announcement comes as a surge in new daily cases fueled largely by the highly transmissible delta variant makes its way through the United States. The country is averaging more than 116,000 new COVID-19 infections a day along with about 50,000 hospitalizations — levels not experienced since the winter surge. 

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About 3% of the U.S. adult population is immunocompromised, according to the CDC. Among them are people with HIV or AIDS, transplant recipients, some cancer patients and people with autoimmune disorders such as rheumatoid arthritis, inflammatory bowel disease and lupus, the CDC explains on its website.

Emerging evidence has indicated people with weakened immune systems could benefit from a booster dose of vaccine in order to bump up their antibody response against the virus. Most recently, a study published Wednesday in the New England Journal of Medicine reported that a third dose of Moderna's COVID-19 vaccine substantially improved protection for organ transplant recipients.

U.S. health officials have long said that people one day might need a booster, as they do for many other vaccines. That’s why studies are underway to test different approaches: simple third doses, mix-and-match tests using a different brand for a third dose, or experimental boosters tweaked to better match different variants.

Fauci added on Thursday during an interview with NBC’s "Today" that most people will "inevitably" need a booster dose in the future.

"No vaccine, at least not within this category, is going to have an indefinite amount of protection," Fauci said. 

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Meanwhile, Israel has already started giving boosters to older adults. Several other countries, including Germany, Russia and the U.K., have approved them for some people. But the head of the World Health Organization recently urged wealthier nations to stop administering boosters to ensure vaccine doses are available to other countries still struggling to administer the first shots. 

COVID-19 shots weren’t studied in large numbers of people with weak immune systems. But limited data and experience with flu and pneumonia vaccines suggest they won’t work as well as they do in others. But experts say the shots should still offer some protection. 

It’s why vaccinations are still recommended for people with immune systems weakened by disease or certain medications. It’s also important that family, friends and caregivers get vaccinated, which will make it far less likely that they pass on the virus.

"It’s prudent to use all the precautions you were using before you were vaccinated," said Dr. Ajit Limaye, a transplant expert at the University of Washington Medicine in Seattle.

Although most cancer patients should get vaccinated as soon as they can, people getting stem cell transplants or CAR T-cell therapy should wait at least three months after treatment to get vaccinated, according to guidance from the National Comprehensive Cancer Network. That delay will make sure the vaccines work as well as they can.

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The Associated Press contributed to this report.