Delta Air Lines announced Monday that it will continue blocking out middle seats and limiting capacity on flights because of the coronavirus pandemic.

The extra space will last through April 30, 2021.

"We'll continue to reassess seat blocking in relation to case transmission and vaccination rates," Bill Lentsch, chief customer experience officer of Delta Air Lines, said in a statement.

Delta, which has blocked out seats and limited capacity on flights since last April, is currently the only U.S. airline still blocking out middle seats because of the virus.

ABC News' Gio Benitez contributed to this report.

Some classes at the University of North Carolina have the option to go virtual for nearly two weeks after school officials received hundreds of complaints following Saturday night's crowd that rushed Franklin Street.

"As you are no doubt aware, last night hundreds of Carolina fans -- many, presumably students -- flooded Franklin Street to celebrate our men’s basketball victory over Duke," UNC-Chapel Hill officials said in a statement Sunday.

UNC-Chapel Hill students have agreed to adhere to COVID-19 rules like state gathering restrictions, mask-wearing and physical distancing, according to university officials.

"Those standards do not include exceptions for winning basketball games," the officials said.

The timing of the crowd fell the weekend before students returned for in-person learning for spring semester. While in-person instruction will continue Monday, faculty are allowed to teach virtually and return to in-person learning on Feb. 17, according to the university. Students who attend in-person classes are required to be tested twice a week.

ABC News' Will Gretzky contributed to this report.

The South African government halted its rollout of a COVID-19 vaccine developed by England's University of Oxford and British-Swedish pharmaceutical giant AstraZeneca, following trial results that found the shot provided "minimal protection" against mild-to-moderate sickness from a new, more contagious variant of the novel coronavirus spreading in South Africa.

The trial did not assess whether the Oxford/AstraZeneca vaccine protects against severe illness and death caused by the new variant, known as B1351.

An AstraZeneca spokesperson said the company believes its vaccine will protect against severe disease caused by B1351.

"This was a small study with predominantly young (average 31 years) healthy adults, where severe disease is not predominant. No severe disease or hospitalization was observed in the vaccine or control participants," the spokesperson said in a statement Monday. "We are working closely with the South African Ministry of Health on how best to support the evaluation of COVID-19 Vaccine AstraZeneca against severe disease of the B.1.351 variant, and how to bring this vaccine to the South African people."

ABC News' Zoe Magee contributed to this report.

Athletes will be tested for COVID-19 at least once every four days during their stay in Tokyo at the pandemic-delayed Summer Olympic and Paralympic Games, according to a "playbook" released by organizers Tuesday.

Over the past week, Olympics organizers have released different playbooks for each group of key stakeholders that outline COVID-19 protocols and rules of conduct for before, during and after the Tokyo Games, which are slated to open July 23. The playbook released Tuesday, which is aimed at athletes and team officials, warns that individuals could be kicked out of their events if they break protocols.

In addition to regular testing at the Games, athletes and team officials must take a COVID-19 test approved by the Japanese government within 72 hours of the departure time of their flight to the country, show proof of that negative test upon arrival and be prepared to take another test at the airport. Athletes will be barred from competing at the Games if they test positive for COVID-19.

Athletes and team officials will only be permitted to leave the Olympic and Paralympic Village, or other designated accommodation, to carry out the activities detailed in their "14-day activity plan," according to the playbook. They are not allowed to visit gyms, tourist areas, shops, restaurants and bars, among other places.

The playbook also asks athletes and team officials to keep two meters away from others and avoid "unnecessary forms of physical contact such as hugs, high-fives and handshakes."

The 2020 Summer Olympics were supposed to kick off in the Japanese capital last year on July 24. But in late March, amid mounting calls to delay or cancel the upcoming Games, the International Olympic Committee and Japanese organizers announced that the event would be held a year later due to the pandemic. They have been outwardly staunch in their determination to go forward with the Games ever since, even as Japan -- and much of the world -- face a resurgence of COVD-19 infections.