Employees of Goldman and Jeffries are being asked to get booster shots. The University of Oregon requires students and staff to get boosters. New York State plans to stop considering residents fully vaccine free if they don't get the shots.
Corporations, schools, governments and even sports leagues are rethinking what it means to be "fully vaccine" as the Omicron variant spreads.
Federal health officials have taken on the question. Some policymakers want to encourage Americans to get three doses, but they would like to keep the definition of a phrase that has become important to daily life in much of the country.
Rochelle P. Walensky, the C.D.C. director, said in an interview on Tuesday that she and other health officials were working through that question now.
There isn't a debate about what people should do. If they are eligible for a boost, they should get boosted, according to C.D.C.
Some experts think the time for change has arrived with the rise of Omicron. The executive director of the American Public Health Association thinks the time is right. He said that the additional booster dose is what we should be thinking of as fully vaccine.
Redefining "fully vaccine" could lead to enormous logistical challenges, as even supporters of the idea concede, and it is likely to cause political backlash. Millions of Americans who thought of themselves as vaccine-free could lose access to restaurants, offices, concerts, events and gatherings if they didn't have boosters.
After two years of shifting recommendations, the change risks damaging public health officials' trust. Some Americans may feel that the goal posts have been moved.
The executive vice president of KFF, a nonprofit organization that focuses on health issues, said that a determination of what constitutes full vaccination may be grounded in science, but it has significant political and economic ripple effects.
The C.D.C. defines "fully vaccined" as those who have received two or one dose of the Pfizer-BioNTech or Moderna shots.
The effectiveness of the vaccines against the virus waned over time, despite experts believing that they protect against hospitalization and death. The effectiveness of full vaccination against Omicron is less than had been thought.
A booster dose is likely to shore up the immune system's defenses against the variant, reducing the odds of breakthrough infections, according to emerging research. Israel is testing a second booster in health care workers.
Dr. Robert Wachter, chair of the department of medicine at the University of California, San Francisco, said that the presence of a variant that is smart at evading vaccine has changed the game.
When the science changes, the guidance has to change.
The New York Times has a story about a vaccine clinic in Montgomery County, Pa.
Tracking the number of boosters can be difficult, and the C.D.C. warns that some may be misclassified.
Roughly 140 million Americans who are not boosted, but who are fully vaccined, could be left in limbo if the definition of "fully vaccined" is changed.
Many schools, businesses, governments and other institutions have relied on the definition of "fully vaccine" by the C.D.C. to establish mandates, requiring people to complete their primary vaccine series in order to attend school, dine out or remain employed.
The initial vaccine series is not enough in the new landscape.
He said it was nonsensical to have that mandate and a state of vaccine that was less effective than you could achieve with a completely safe and easy to take additional intervention.
The most effective way to make sure that the public gets the booster shots that they have been urged to get is to change the definition of fully vaccine.
The Biden administration is considering scrapping the term altogether and replacing it with a phrase that says vaccinations should be up-to-date. It is used to describe other vaccine combinations.
Two officials with knowledge of the discussions said that the administration was leaning towards making such a move soon.
Rochelle P. Walensky is the C.D.C. director. She said that C.D.C. is clear on what people should do. They should get boosted if they are eligible.
The director of the Vaccine Education Center at Children's Hospital of Philadelphia said that it depends on the public health goal for vaccinations.
The best protection against Omicron is likely to come from boosters. The original two-shot series should be enough to prevent hospitalization and death for most young people, according to Dr. Offit. The vaccines will hold up if that is the purpose of the vaccine.
Dr. Philip R. Krause, a former top vaccine regulator at the Food and Drug Administration who retired last month, called efforts to redefine full vaccination a distraction from other public health priorities.
The place where the risk is highest is among the elderly, the immunocompromised, people with comorbidities, and those who have had a vaccine. We should be getting the first shots to the unvaccinated and also finding those people for booster shots.
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The U.S. record for daily coronaviruses cases has been broken as two highly contagious versions have spread across the country. On Tuesday, the seven-day average of U.S. cases topped 267,000.
The C.D.C. reduced the time that certain Americans must stay home from 10 to five days. The change only applies to those without symptoms or who have other symptoms improving.
Changing the definition of fully vaccine is likely to intensify legal challenges. The courts have already rejected the Biden administration's attempt to mandate that large employers require employees to be vaccine free.
He said that requiring all workers to be boosted soon may not be feasible in industries that are already struggling with labor shortages.
It would be chaos in the workplace if so few Americans got a third shot because they wouldn't be up to date. It would take quite a bit of time to implement a requirement for boosters.
Those who have received their primary vaccine series and those who have received no vaccine at all would be lumped together.
Some companies and state officials are still going ahead with booster requirements.
Goldman Sachs will require all eligible employees to get booster shots by February 1. People going to the New York office of the investment bank will have to have boosters by the end of January, according to a memo sent to staff.
The company's chief executive, Rich Handler, and its president, Brian Friedman, wrote in a memo to staff that this will not just be about the company.
The University of Oregon will require students, faculty and staff to get boosters by the end of January, joining a growing list of institutions with similar requirements. The University of Massachusetts had a similar requirement on Wednesday.
New York Gov. Kathy Hochul plans to change the definition of "fully vaccined" to include having a booster shot. In November, the governor of Connecticut said that residents should not consider themselves vaccine-free unless they had boosters.
It may not make sense for employers to require each new recommended shot, as booster recommendations may need frequent revision, as new variant appear and time passes, said Dr. Camille Kotton, an infectious disease physician at Massachusetts General Hospital and an adviser to the C.D.C.
Changing the definition could encourage some Americans to get boosters, but it could also cause opposition to vaccination among those who have not received any.
Dr. Benjamin supports changing the definition despite the challenges.
A redefinition would lump together two different groups, one of which has received their primary shots and the other who has not.
She said that if these groups were lumped into a new unvaccinated-partially-vaccinated category, it would make it more difficult for researchers to track important public health data.
Ensuring that 38 percent of Americans who have not completed their primary vaccine series should remain the top priority.
Emma Goldberg was involved in reporting.
