Labor unions may soon find themselves in an unexpected role during the coronavirus pandemic: defending members who refuse to take a vaccine.

Unions have fought hard to get their workers near the top of the vaccination list but now are girding for the likelihood that some of their members will push back on businesses that mandate shots for employees.

The brewing standoffs carry political implications as well as public health concerns. During the 2020 campaign, unions were largely supportive of President Biden, who has set a goal of 100 million vaccinations in his first 100 days in office.

Kim Cordova, vice president of the United Food and Commercial Workers International Union (UFCW), said companies have to negotiate with unions before making any vaccine mandatory.

“If the employer wants to make that mandatory ... they would have to negotiate that with us. They could not change a condition of employment. They could not make that mandatory in the middle of a contract unless the state or the government required it,” she said.

The UFCW, which represents 1.3 million grocery, food processing and health care workers, has pushed for states to prioritize their members in vaccine distribution.

“Obviously, we want priority, but we also want freedom of health care choices,” Cordova said, adding that she expected that some workers, because of allergies or religious objections, won’t want to take the vaccine.

If a union employee’s contract doesn’t specifically address vaccinations or include anything like medical testing and vaccines, the dispute becomes an issue of mandatory bargaining, experts said.

“If you unilaterally implement a mandatory vaccine policy when it’s not been addressed in your current collective bargaining agreement, that may lead to a successful unfair labor practice charge against the employer,” said Jill Lashay, a labor law expert at Buchanan Ingersoll & Rooney PC who represents management and employers.

Lashay is co-author of a report on mandating the COVID-19 vaccine that concluded different rules may apply for mandating a vaccine for employers with union members, even if taking it could be considered essential for the job.

Jay Timmons, CEO of the National Association of Manufacturers, previously told The Hill that his group would back member companies implementing vaccination requirements.

Some unions sidestepped questions about whether they would defend members who refuse to take the COVID-19 vaccine.

“While we support universal vaccination, we believe the most effective approach is to encourage our members to make informed decisions. Our view is that if workers are properly educated, they will make the decision that is best for them, their colleagues, their families and their communities consistent with their own personal beliefs and health status,” said Lee Saunders, president of the American Federation of State, County and Municipal Employees, the largest public sector union in the U.S.

Forty-six percent of respondents said last month that they intend to take the vaccine as early as possible, up 20 percentage points from a similar poll in late October, according to a USA Today-Suffolk University survey.

Meanwhile, 32 percent of people polled said they were willing to wait for others to get the shot first, and 20 percent were unwilling to take it at any time, a number that hasn’t changed from October.

The American Federation of Teachers, which represents 1.7 million educators, said in October that it plans to focus on educating its members about the importance of vaccinations.

“Employee education that includes the risks and benefits of the vaccination, as well as the known efficacy rates of the vaccine; and an informed declination for those who opt out after receiving education as described above,” the union’s executive council said in a resolution adopted in October.

The resolution focuses on negotiations with employers to make sure the COVID-19 vaccine is convenient and readily available for employees.

The union would not say whether it will back any members who refuse to take the vaccine.

The challenge ahead is comparable to the flu vaccination, which some companies already require their employees to take. Lashay said employers are likely on firm legal ground if the existing collective bargaining agreement permits mandatory vaccines. But some are more specific and could have clauses for illnesses like the flu.

In addition to potential clashes with union members, employers could run into issues with workers under the American Disabilities Act and Title VII of the Civil Rights Act of 1964, which allows for employee vaccination exemptions for certain health and religious reasons.

Richard Block, labor and employment law attorney at Mintz, Levin, Cohn, Ferris, Glovsky and Popeo P.C., said employers should communicate with their unions if they want to mandate the COVID-19 vaccine.

“It seems to me that if an employer sits down and discusses it with the union, and is flexible enough to make some exceptions, that they may succeed in getting a mandatory program across. Those exceptions, they could be people with disabilities, it could be people with religious objections, but I think the gray area is just going to be people who feel it’s unsafe,” said Block, whose clients include Fortune 500 companies, financial institutions and health care organizations.

The issue isn’t black and white, he said, because many union members want the vaccine and want their co-workers to get it so that the workplace is safer.

“This is going to be a really fascinating bargaining subject because you don’t have to be a management-sided person to think that it’s reasonable to have your workforce vaccinated,” he said.

For some unions, though, that decision should be left to the individual.

“Some people may just not want to do it,” Cordova, of UFCW, said. “There are some people who just don’t have confidence in the vaccine yet. The problem is everything has been made so political.”