Coronavirus news: University imposes quarantine for all students

Miami University in Ohio reported 159 new cases of the coronavirus over the Labor Day weekend, bringing the university's total number of cases to 1,037 in the last two weeks, according to a school dashboard.

Over the long weekend, six Miami University students were cited for breaking the city’s ordinance against large gatherings, ABC Cincinnati affiliate WCPO reported.

The students told police they tested positive for COVID-19 and were supposed to be quarantining, WCPO reported.

ABC News' Ahmad Hemingway contributed to this report

No trick-or-treating is allowed this Halloween in Los Angeles County due to the pandemic, ABC Los Angeles station KABC reported

The health department said it's too difficult to maintain social distancing with door-to-door trick-or-treating.

Parties, haunted houses and "trunk or treating" -- when kids go from car to car instead of house to house -- are also not allowed.

Car parades, dressing up houses and Halloween-themed meals at outdoor restaurants are permitted, the Department of Health said.

California has the most coronavirus cases of any state in the U.S., with over 745,000 people diagnosed, according to Johns Hopkins University data.

Over 249,000 of California's cases are in Los Angeles County, according to county data. At least 6,036 people in the county have died.

A private university in central Illinois is requiring its entire student body to quarantine for two weeks and is temporarily reverting to remote learning due to clusters of COVID-19 cases on campus.

Bradley University in Peoria, Illinois, has confirmed just under 50 positive cases on campus so far, according to the school's president, Stephen Standifird, who expressed concern over seeing "both large and small gathering where masks and physical distancing are not observed."

"Although it may seem extreme, this move to temporary remote learning and a two-week, all-student quarantine allows us to focus on the continuity of the educational experience for all of our students while giving us time to gather data on the full extent of the spread of the virus and assess the best way to proceed as a community," Standifird said in a message to students Tuesday.

From Tuesday, the school is requiring students to limit nonessential interactions, stay in their residence halls or off-campus housing and take classes remotely.

"This two-week quarantine creates an opportunity for us to reset our behaviors so we can have a successful semester," Standifird added. "I still think it’s possible for us to do so. We would not engage in the two-week quarantine if I did not believe it was possible for us to complete the semester on campus successfully, but this only happens if we collectively change our behaviors moving forward."

Bradley University currently enrolls nearly 6,000 students in undergraduate and graduate programs, according to its website.

The U.K. Medicines and Healthcare products Regulatory Agency (MHRA) said it is "urgently reviewing all the information and actively engaging with the researchers to determine whether the trial should restart as quickly as possible," following news that AstraZeneca had paused its COVID-19 vaccine study being conducted with England's University of Oxford due to what the pharmaceutical company described as a "potentially unexplained illness in one of the trials."

The government body is responsible for deciding when the trial can resume.

"Participant safety in any clinical trial is our top priority," said Dr. Siu Ping Lam, the MHRA's director of licensing division, said in a statement Wednesday. "We are working with the Oxford Vaccine Centre following the temporary pause of their COVID-19 vaccine trial to allow for the review of safety data. This is in line with the authorized protocol for the trial."

The University of Oxford wouldn't give details on the participant's condition or whereabouts, citing patient confidentiality.

"Whilst it has been reported that one trial volunteer has become ill, this may be due to an issue related to the vaccine. It also may not," a university spokesperson told ABC News Wednesday morning.

During an interview with Sky News on Wednesday, British Secretary of State for Health and Social Care Matt Hancock revealed that it's not the first time the trial has been halted.

"It's not actually the first time it has happened to the Oxford vaccine and it's a standard process in clinical trials," Hancock said. "There was a pause earlier in the summer and that was resolved without a problem."

ABC News' Zoe Magee contributed to this report.