After months of teaching online, Cynthia Core was looking forward to being back in the classroom this fall. But over the summer, with news of the delta variant surging and cases of breakthrough infections among vaccinated people, and with a school that wasn’t requiring masks on campus, she began to worry.

Her classroom has no windows and isn’t large enough for students to spread out much. Over a two-and-a-half-hour speech-language pathology class, she wondered, wouldn’t there be a risk to everyone in there?

Core is vaccinated, as the school requires for faculty, staff and students, and George Washington University recently added a mask mandate, which alleviated the worst of her concerns.

But she can’t stop thinking about her parents, who are medically vulnerable and whom she will help to care for this fall, wondering if her exposure to so many people from all over the country might endanger them. “If I get the virus and pass it on to my parents,” she said, “that would be really horrible.”

With students returning to college campuses across the country for in-person classes after a year of pandemic disruptions, many faculty members describe a mix of hope and fear as they weigh the fast-changing science of covid-19. With the help of coronavirus vaccines, this fall was supposed to be the joyful return to campus traditions after so many months of isolation, restrictions and stuttering Zoom connections. But now many feel uncertain that resumption of normal routines is safe.

“It’s really unknown what will happen next week,” when classes resume in person, said Eric Chicken, a professor of statistics and the president of the faculty senate at Florida State University. “It’s a big concern for faculty.”

The circumstances — and faculty opinions — vary widely. Some professors are fearful because their universities face state bans on vaccine mandates and have large populations of people hesitant or unwilling to get the shots. Some are preparing to teach knowing most students will be vaccinated and wearing masks, but worry they wouldn’t be allowed to switch to virtual teaching if there were an outbreak. Some feel comfortable with the conditions for themselves but are anxious about passing the infection on to unvaccinated young children or immunocompromised family members.

And some professors object to masking and vaccine requirements, finding the mandates heavy-handed and obtrusive.

Pervading everything is a weariness with the virus, and a longing for more stable, certain times.

At Spelman College, the university’s faculty council sent a message to students Thursday saying faculty members had decided not to teach in person because of safety concerns. After the administration submitted safety guidelines and committed to continuing to work with faculty to make sure safety protocols are enforced, the faculty decided to return to full in-person instruction beginning Monday, according to Jazmyn Burton, a spokeswoman for the university.

At Arkansas State University, Leah Long, an instructor, said she had made the wrenching decision to resign from a job she loved. She had been looking forward to teaching in person again but felt the university didn’t seem to be taking enough steps to prevent infections from spreading. She didn’t want to put her 3-year-old son in a day care that has had multiple covid cases and unvaccinated teachers, and was worried about working in a place where cases are surging. Less than 40 percent of eligible people are fully vaccinated in the state, according to a Washington Post analysis.

This month, the university began requiring people to wear masks indoors if they couldn’t maintain a six-foot distance from others (other than in student housing). School officials encouraged people to get vaccinated.

Long said she was told she would not be allowed to teach virtually.

“The whole state, they’re just acting like there’s no problem,” Long said. “A lot of people don’t have young kids, and don’t feel like it’s a big danger.”

But to her, it felt like a very unsafe situation. “I just can’t do it,” she said. “It’s a bridge too far.”

“We understand the continued challenging circumstances faced by people during this global pandemic,” said Bill Smith, spokesman for Arkansas State University. “While we are prohibited by state law from mandating vaccines for our employees and students, we have strongly encouraged, and will continue to strongly encourage, everyone on campus to be vaccinated. We have taken other steps as well, such as imposing a mask requirement on campus and establishing reporting protocols that will hopefully mitigate against the spread of this deadly virus.”

In North Carolina, 500 faculty members signed a petition calling for the University of North Carolina at Chapel Hill to begin the year with virtual classes, citing the number of hospitalized patients and full or nearly full intensive care units. “The current plan for UNC — which includes no ‘off-ramp’ for remote learning, unlike last fall, and no vaccine mandate — is for regular classrooms with no physical distancing, near-full dorms, football games with no masks, and full-to-capacity dining halls. This is a formula for disaster,” they wrote.

Classes began Monday in person, and Joanne Peters Denny, a spokeswoman for the university, said there are layers of protections in place. Eighty-seven percent of students have attested they’re vaccinated, she said, and those who are not will be tested twice weekly. At a recent meeting, the university’s chancellor, Kevin M. Guskiewicz, said: “We don’t believe that we have to choose between safety and in-person learning, we can do both with the right approach.”

At Pennsylvania State University, a group of faculty members protested last week, calling for a vaccine mandate on campus, the Daily Collegian newspaper reported.

“My class that starts on Monday has 590 people in a single room,” James Tierney, an assistant teaching professor of economics at Penn State, said by phone, “which I don’t think is the best idea for a global pandemic.” His biggest concern was the educational inequity that would be created, he said, for the many students he expects will have to be quarantined because they’re infected or because they were in close contact with someone who had the virus.

He told school officials that he would allow students to take the class virtually — and that he was resigning, effective at the end of this calendar year. The school’s covid policies weren’t the only reason, but they were the breaking point for him. He wasn’t happy, he said, with university leaders “trying to assure us they’re doing everything possible, when it’s clear they’re not.”

Last week, Penn State President Eric Barron wrote in a letter to campus that pandemic rules are polarizing, with many opposing mandates and others calling for them — and that state funding for the university is reliant on bipartisan support. Barron wrote they would take further steps if needed to prevent the spread of the coronavirus on their campuses.

At the University of Minnesota, Carol Chomsky, a professor of law, said: “There’s been a lot of — as everywhere — concern about health coming back to campus.” Since people won’t know which colleagues or students are vaccinated, “there’s just generalized anxiety about it,” she said. “It’s just an uncertain environment for what that means for infection.”

Some professors and groups have pressed for a vaccine mandate on campus, she said, and conditions are evolving. (The university will require students to get vaccines when they gain full FDA approval.) Personally, Chomsky said she feels much more comfortable than she did last fall, because she is vaccinated and expects most of her law students will be, as well. “I still haven’t figured out what I’ll do about in-person meetings in close quarters,” she said. “But I’m feeling much more protected given my vaccination status. I’m glad to be headed back to in-person teaching …

“There’s no way to protect against absolutely every risk. I don’t think it’s possible.”

At Florida State University, Chicken said, “the concern I’m hearing from faculty is with the delta variant, even fully vaccinated people can be carriers.” The administration has been trying to help faculty, he said, but “the state of Florida is really tying our hands in what we’re doing.

“ … We expect students to be vaccinated and wear a mask,” he said. “That’s the strongest language we can use — we can’t require it.”

Since that’s going to be an issue, he said, many faculty want an option to be able to teach remotely again. While others are looking forward to getting back in the classroom, people who are at risk or have family members at risk, are pushing for the option, he said.

Amy Farnum-Patronis, a spokeswoman for the university, said that they share the desire for a safe academic environment and that faculty and staff can give feedback at a town hall next week with the school’s president.

Chicken said they plan to emphasize the mask recommendation in syllabi and other places, and remind students not to come to class if they feel sick.

“We’re concerned. My family is concerned,” he said, as students converge on campus. “We’ll be as careful as we can.”