International students are returning to U.S. colleges in stronger numbers this year, but the rebound has yet to make up for last year’s historic declines as COVID-19 continues to disrupt academic exchange, according to a new survey.

Nationwide, American colleges and universities saw a 4% annual increase in international students this fall, according to survey results released Monday by the Institute of International Education. But that follows a decrease of 15% last year — the steepest decline since the institute began publishing data in 1948.

The upturn is better than many colleges were forecasting over the summer as the delta variant surged. But it also reflects continued obstacles as visa backlogs persist and as some students show reluctance to study abroad during the pandemic.

Universities and U.S. officials hope this year’s uptick is the start of a long-term rebound. As international travel ramps up, there’s optimism that colleges will see growth past their pre-pandemic levels.

“We expect a surge following the pandemic,” Matthew Lussenhop, an acting U.S. assistant secretary of state, told reporters. This year’s increase indicates that international students “continue to value a U.S. education and remain committed to pursuing studies in the United States,” he added.

Overall, 70% of U.S. colleges reported an uptick in international students this fall, while 20% saw decreases and 10% remained level, according to the institute. That’s based on a preliminary survey of more than 800 U.S. schools. The nonprofit plans to issue full nationwide data next year.

At least some of the increase is due to new students who hoped to come to the U.S. last year but delayed their plans because of the pandemic. All told, there was a 68% increase in newly enrolled international students this year, a dramatic increase compared with last year’s decrease of 46%.

For many schools, even a modest upturn is a relief. Over the summer, officials at U.S. universities worried that the delta variant would dash any hopes of a rebound. But for many, that did not come to pass.

In August, U.S. embassies and consulates in India reported that they had recently issued visas to a record 55,000 students even after starting the process two months late because of COVID-19. Embassies in China reported that they had issued 85,000 student visas.

At the University of Illinois at Urbana-Champaign, more than 10,000 international students enrolled this fall, which nearly offsets a 28% decline from last year.

“What we’re seeing now is a return to normal for our international populations,” said Andy Borst, director of undergraduate admissions at the university. The rebound is fueled by new undergraduates, with those from India up nearly 70% over pre-pandemic levels.

“We just had this pent-up demand,” Borst said. “A lot of Big Ten schools saw increases beyond what we were expecting.”

At some schools with big brands overseas, enrollments rebounded past their 2019 figures. More than 17,000 international students enrolled at New York University this fall, up 14% over 2019, according to school data.

At the University of Rochester, another top destination for international students in New York, enrollments from abroad surged 70% over 2019 levels, driven by a boom in graduate students, according to school data.

Most students were able to arrive on campus within the first weeks of the semester, but many dealt with visa backlogs at U.S. embassies and consulates, not to mention costly flights and cancellations, said Jennifer Blask, the university’s head of international admissions.

The vast majority of U.S. colleges returned to in-person learning by this fall, but not all international students are physically on campus. After last year’s shift to remote learning, many schools have continued offering online classes to students abroad, allowing thousands to stay enrolled from afar.

Out of all international students enrolled at U.S. colleges this year, the survey found that about 65% were taking classes on campus.

For Chinese students unable to arrive for this semester, NYU is continuing to let them use its academic center in Shanghai, which is traditionally for U.S. students studying abroad. The university also let international students use its London and Abu Dhabi locations last year, but has since returned them to use for study abroad programs.

For some colleges, the new flexibility of online learning helped avoid further enrollment setbacks. In the past, students at the University of San Francisco might have been able to start the term a week late if they faced visa or travel problems. Now, those facing visa delays can arrive halfway through the term or later, and in the meantime study online from abroad.

Facing travel restrictions inside Vietnam, graduate student Vinh Le was unable to get to Ho Chi Minh City’s airport in time for the start of fall classes. Instead, he studied online for more than two months until he could get his first vaccine shot, which allowed him to travel.

Taking classes online was challenging because of the time difference, he said, but professors were “very supportive” and recorded their lectures to be watched any time. He ended up making it to the University of San Francisco on Nov. 1.

International students are seen as important contributors to U.S. campuses for a variety of reasons. Colleges say they help provide a diverse mix of cultures and views on campus. Many end up working in high-demand fields after graduating. And some colleges rely on the financial benefits of international students, who are typically charged higher tuition rates.

Although many colleges have avoided a second year of declines, there’s still concern that the upturn may be isolated to certain types of colleges. The new survey found that, last year, community colleges suffered much steeper declines than four-year universities, with a 24% backslide nationwide.

Researchers are still analyzing this year’s data, but some worry that community colleges may continue to lag behind.

There are also questions about whether the rebound will continue past this year. New vaccine requirements for foreign travelers could make it harder for some students to get here, and colleges are expecting continued competition from colleges in Australia, Canada and other nations looking to boost their international populations.

Still, officials at many colleges are optimistic. More vaccines are being sent overseas, and newly lifted travel bans promise to reduce barriers to travel. Some also credit President Joe Biden for sending a message that America wants students from abroad.

In July, the administration issued a statement promising a “renewed” commitment to international education, saying it would work to make overseas students feel welcome.

Rachel Banks, senior director of public policy and legislative strategy for NAFSA, an international education association, said that’s a shift from the Trump administration.

“In the last administration, there was a lot of negativity and negative rhetoric around international students,” Banks said. “Biden is now trying to telegraph to the world that there’s interest in having international students coming here.”