WASHINGTON – Biden government health officials increasingly believe that vulnerable populations will need a booster dose even as research continues into how long coronavirus vaccines will remain effective.

Senior officials now say they believe that people over 65 or with compromised immune systems will most likely need a third vaccination from Pfizer-BioNTech or Moderna, two vaccines based on the same technology that were used to vaccinate the vast majority of Americans until now. That’s a significant shift from a few weeks ago when the government said there wasn’t enough evidence to support boosters.

On Thursday, a key official with the Centers for Disease Control and Prevention said the agency is looking into ways to give immune-compromised patients a third dose before regulators expand emergency approval for coronavirus vaccines, a move soon for Pfizer vaccination could be done.

Dr. Amanda Cohn, the chief medical officer of the CDC’s immunization division, told an agency advisory committee that officials are “actively seeking ways” to give certain people access to booster vaccinations “sooner than any possible change in government decisions”.

“So stay tuned,” she added.

The growing consensus within the government that at least some Americans need a booster dose is in part to do with research suggesting that the Pfizer vaccine is less effective against the coronavirus after about six months. More than half of those fully vaccinated in the United States to date have received Pfizer’s vaccine in two doses three weeks apart.

Pfizer’s ongoing global study of its clinical trial participants shows the vaccine’s effectiveness against symptomatic infections drops from a peak of 95 percent to 84 percent four to six months after the second dose, the company said.

Data from the Israeli government, which has fully vaccinated more than half of its population with doses of Pfizer since January, also suggests a downward trend in efficacy over time, though administrative officials view these data cautiously due to the large margin of error.

The latest figures from the Israeli Ministry of Health, released later this week, suggest that Pfizer’s vaccine was only 39 percent effective in preventing infections in the country in late June and early July, compared with 95 percent from January through April.

The vaccine remained more than 90 percent effective in preventing serious illnesses and almost as effective in preventing hospital stays. Israel began offering a third dose of Pfizer to citizens with severely compromised immune systems on July 12th.

Dr. Anthony S. Fauci, who heads the infectious diseases division of the National Institutes of Health, said he was surprised at the apparently steep drop in the effectiveness of the Pfizer vaccine suggested by the Israeli data. He said he wanted to compare it to data the CDC has collected from cohorts of thousands of people in the United States. “People raise their eyebrows a little,” he said.

While other questions abound, senior administrative officials said it was becoming increasingly clear that the vaccines would not provide unlimited immunity to the virus and that at least some people might need booster sessions nine months after their first vaccination. The government has already purchased more than enough vaccine to deliver the third dose of Pfizer and Moderna and has been quietly preparing to step up distribution efforts if necessary.

With so little data left public, many health officials and experts have spoken cautiously about booster vaccinations. Dr. Paul A. Offit, a member of the Food and Drug Administration’s external advisory committee of vaccine experts, said an increase in mild or moderate cases of Covid-19 in people who have been vaccinated does not necessarily mean that a booster is needed.

“The goal of this vaccine is not to prevent mild or mild, moderate infectious diseases,” he said. “The aim is to prevent hospitalization until death. At the moment this vaccine has withstood that. “


July 23, 2021, 10:06 p.m. ET

An early prospect of a third dose could also act as a deterrent against vaccination, warn other health experts. If Americans feel that immunity to the vaccines is short-lived, they are less likely to get their first vaccination.

“We don’t want people to believe that the vaccines are not effective when you talk about booster vaccinations,” said Dr. Fauci at a hearing before Congress on Tuesday. “You are highly effective.”

Among vaccine manufacturers, Pfizer has been particularly proactive in sharing its data with the government. But the government was stunned by the company’s public announcement earlier this month that it was planning to seek emergency FDA approval for a booster vaccination.

The company said early data from its booster study showed neutralizing antibody levels in clinical trial participants who received a third dose six months after the second was five to 10 times higher than those in recipients who received two doses.

Fearing that the American public would get the wrong news, the FDA and CDC responded with an unusual public statement: “Americans who have been fully vaccinated don’t need a booster right now.” They added, “We are prepared for booster doses, if and when science shows they are needed. “

Ordinarily, the FDA would approve the use of a booster, perhaps after a meeting of its external advisory committee. Then the CDC, which has its own advisory committee, would have to officially recommend it, said Dr. Offit.

Understand the state of vaccine mandates in the United States

But if the FDA fully licensed a vaccine, doctors would have much more leeway to prescribe a booster to their patients. Some health experts believe Pfizer could get this approval by fall this year.

At the CDC advisory board meeting on Thursday, Dr. Cohn, the medical director of the vaccines division, suggested that it might be possible to offer booster shots to people with compromised immune systems through a trial study or other means without waiting for the FDA

Dr. Camille Kotton, an infectious disease expert at Massachusetts General Hospital, told the panel that some patients, especially those who are more educated or “able to look after their own health care,” manage to get a third dose on their own, despite lack of green light from the government.

“Many took matters into their own hands,” she says. “I’m worried they might do this unattended,” she said, while the doctors’ hands are tied due to the lack of regulatory approval.

According to the CDC, people with a weakened immune system make up 2.7 percent of the population and include cancer, organ or stem cell transplants or HIV.

At the Senate Health Committee hearing Tuesday, several senators questioned administration health officials about how quickly they would act on the booster issue. Senator Mitt Romney, a Republican from Utah, said he was unhappy that officials couldn’t come up with a better schedule.

Senator Richard M. Burr, a Republican from North Carolina, noted that Israel is already offering a third chance to some of its most vulnerable citizens. “Why don’t we make the same decisions?” he asked.

Dr. Rochelle Walensky, the director of the CDC, testified that scientists studied the effectiveness of the vaccines in tens of thousands of people, including nursing home residents and more than 5,000 key workers.

“Fortunately, we expect this to wear off, not go down,” she said of her effectiveness. “As we see that fade, we will – this will be our time to act.”

Pfizer is expected to soon publish its clinical studies on immunity declining and the benefits of booster shoots in articles in a peer-reviewed journal. Moderna hasn’t released any data on booster studies, officials said.

Johnson & Johnson’s single-use vaccine has so far played a minor role in the country’s vaccination campaign. Clinical trial data on the mode of action of this two-shot vaccine is expected next month.

Noah Weiland contributed the reporting.