As cases of COVID-19 rise throughout the U.S., health officials warn that an increasing number of fully vaccinated people are being hospitalized or going to the emergency room. The concern about waning immunity against severe COVID-19 infection comes as the Food and Drug Administration is expected to authorize a Pfizer-BioNTech vaccine booster shot for all adults 18 and older.
“What we’re starting to see now is an uptick in hospitalizations among people who’ve been vaccinated but not boosted,” Dr. Anthony Fauci, the director of the National Institute for Allergy and Infectious Disease, said Tuesday in an interview. “It’s a significant proportion, but not the majority by any means.”
On Wednesday, Dr. Rochelle Walensky, the director of the Centers for Disease Control and Prevention, reported a decline in vaccine effectiveness among the elderly and residents of long-term care facilities, many of whom were the first to be eligible to be vaccinated last winter.
“Although the highest risk are those people who are unvaccinated, we are seeing an increase in emergency department visits among adults 65 and older, which are now again higher than they are for younger age groups,” Walensky said Wednesday at a White House COVID-19 briefing.
Walensky also pointed to new data on long-term care facilities from the agency's National Healthcare Safety Network comparing rates of COVID-19 disease between people who are vaccinated with two doses and those who have received extra doses.
“The rate of disease is markedly lower for those who received their booster shot, demonstrating our boosters are working,” she said.
Fauci and Walensky stressed that the majority of hospitalizations and deaths are still among unvaccinated people in the U.S.
"Studies show that those who are unvaccinated continue to be more likely to be infected, more likely to be in the hospital and more likely to have severe complications from COVID-19," Walensky said at the briefing.
The current seven-day rate of hospital admissions is about 5,300 per day, according to the CDC, and about 1,000 people in the U.S. are dying from COVID-19 every day.
Still, it’s not clear how many breakthrough hospitalizations there are. Although the CDC has been tracking the rate of hospitalizations among fully vaccinated people, its website shows data only through Aug. 28. According to the latest data from the CDC, an unvaccinated person is at 11 times greater risk of dying from COVID-19 than a vaccinated person.
The CDC didn’t respond to a request for new numbers.
At least 31 million people have received extra doses of a Pfizer, Moderna or Johnson & Johnson vaccine, according to the CDC.
Should younger adults get booster doses?
Fauci pointed to data from Israel that show a major improvement in protection against severe disease and hospitalizations in those who have had boosters compared to those who haven’t. In a study published last month, Israeli researchers found a twentyfold reduction in severe disease among those over 60 who got booster shots.
Another study last month from Israeli researchers and faculty members of Harvard Medical School found that booster doses were 92% effective at preventing severe disease when compared to having received a standard two-dose regimen at least five months previously.
As vaccination rates increase in the U.S., it’s expected that more vaccinated people would be hospitalized with COVID-19, simply because the vaccines aren’t 100% protective against severe illness, Fauci said.
“That’s where we get back to the importance of getting a boost,” Fauci said. “It will dramatically diminish the likelihood that if you do get infected with a breakthrough infection that you’ll wind up in the hospital.”
The U.S. is only starting to see “inklings” of waning protection against severe disease, Fauci said — but Israel has been about six weeks ahead in COVID-19’s development throughout the pandemic, one reason federal health officials have relied on its data.
“If you look strictly at the data from Israel, it’s very clear that the differences in immunity waning is much more profound in the elderly, but it goes across the board,” Fauci said, noting that, in particular, people over 40 who have had boosters showed marked improvement in protection against severe disease.
Given the lack of national data on breakthrough illnesses among younger adults, it’s unclear how many cases of severe disease there have been and whether boosters would provide a benefit.
“I wouldn’t be surprised that sooner or later, you’re going to see the data indicate that it’s also going to be very important for (younger) people, when they have boosters available, to get the booster shot,” Fauci said.
Dr. Bob Wachter, the chair of the University of California, San Francisco, department of medicine, would like to expand boosters to all adults over 18.
“It was reasonable to start boosting with people at the highest risk of a bad outcome or the highest risk of exposure,” Wachter said. “However, we’ve sort of gone through that stage, and there’s enough vaccine around.”
One of the biggest questions surrounding booster doses was a potential risk of inflammation of the heart muscle, or myocarditis, which has been associated with the mRNA vaccines, especially in young males. Israeli health officials report that no significant signals of myocarditis have emerged yet, Fauci said.
Along with the push for boosters, giving first doses to the unvaccinated is critically important, experts say.
Dr. Paul Sax, a professor of medicine at Brigham and Women’s Hospital and Harvard Medical School, said getting people their first doses and others booster doses can absolutely happen at the same time.
“They’re separate processes and seem to be not in conflict with each other,” Sax said. “We can definitely do both, because I think most of the people who are vaccinated would agree to a booster dose if it meant they’d be better protected."
Sax is also strongly in favor of widening booster doses to include all adults over 18.
“It’s inevitable and in my opinion the right move,” he said. “It does appear that two doses just isn’t sufficient.”
This was originally published on NBC News. Patrick Martin and Marina Kopf contributed to this story.