Thousands of American workers face possible job losses as requirements to be vaccinated against COVID-19 begin to be enforced.

The vaccine requirements, known as mandates, from governments and companies have faced opposition across the country. But they have also been effective at persuading many workers to get vaccinated.

COVID-19 has killed more than 700,000 people in the United States. U.S. officials say about 77 percent of individuals who are eligible for a vaccine have received at least one shot.

One of the latest public disputes over the issue happened this week at Washington State University (WSU). The university's head football coach was fired along with four assistants for failing to obey the state's vaccine requirement. The coach, Nick Rolovich, had sought a religious exception to the rule earlier this month.

School officials said the vaccine requirement is aimed at protecting the safety of its teachers and students. "Experience is showing that vaccine mandates help motivate people to complete the vaccination process," said Marty Dickinson, who heads WSU's Board of Regents.

However, the mandates are causing concern about worker shortages across several industries.

Thousands of police officers and firefighters in cities like Chicago and Baltimore are at risk of losing their jobs soon. They are facing rules that require them to report whether they are vaccinated.

In Chicago, Mayor Lori Lightfoot has been battling with the city's police labor union. It does not support the vaccine mandate for city workers. About one third of the city's 12,770 police employees failed to report their vaccination status last week as required. Some officers have had their pay cut off.

Lightfoot has said the mandate is aimed at "saving lives" and creating a safe workplace. She accused the union of trying to start an "insurrection" by opposing the rule.

The administration of President Joe Biden has been behind the push to get more Americans vaccinated.

Last week, about 200 Boeing Company employees and others held a protest. They oppose the airplane maker's requirement that 125,000 workers be vaccinated by December 8. That rule is linked to an executive order issued by Biden for federal contractors.

The rules for another order covering private businesses with 100 or more employees are expected to be finalized soon.

Along with the mandate for federal workers and contractors, Biden's vaccine requirements will affect about 100 million people. That is about two-thirds of the U.S. workforce.

A series of layoffs has already moved through the healthcare industry. The industry acted faster than others to put vaccine mandates in place.

Nurses and other healthcare workers who chose to leave their jobs rather than be vaccinated recently spoke to Reuters news agency. They said they were concerned over a lack of long-term data about the three vaccines currently available in the U.S.

The vaccines received emergency use approval from the Food and Drug Administration in less than a year. Most medical experts have said they are safe. They have supported their statements by noting large vaccine trials and saying hundreds of millions have received injections worldwide.

Some companies are taking steps to reassure workers that their requests for medical or religious exceptions will be given serious consideration.

Southwest Airlines spoke to its employees last week. The company said it would permit the unvaccinated to continue working rather than being placed on unpaid leave. Southwest said that would be the case if the requests for exceptions have not been examined by the government's December 8 deadline.

I'm Bryan Lynn.

Reuters reported this story. Bryan Lynn adapted the report for VOA Learning English. Mario Ritter, Jr. was the editor.