The city of Portland will require that all of its employees receive a COVID-19 vaccine or submit to weekly testing, a spokeswoman said Sunday.

The vaccination mandate goes into effect Sept. 10 for nonunion employees, but the date is yet to be determined for employees in unions that want to bargain the issue, spokeswoman Jessica Grondin said.

It was not clear Sunday night how many employees could be affected by the mandate and what consequences those who refuse to get vaccinated or be subject to weekly testing might face.

But it appears that Portland is about to become the first city or town in the state to require vaccinations for its employees, according to the Maine Municipal Association.

“I do not know of any other municipalities that have followed Portland in mandating vaccines or testing,” Cathy Conlow, executive director of the MMA, said in an email Sunday evening. “In the absence of a state or federal vaccination mandate for municipal employees, it would be within the purview of the individual municipalities to decide their own policies regarding mandated vaccinations and testing.”

Conlow, the former city manager of Bangor, became the MMA’s new leader this month, replacing Steve Gove.

Portland’s announcement comes as Gov. Janet Mills is set to require vaccination for health care employees in hospitals and nursing homes around the state. Some Portland city employees already will be covered by the governor’s mandate, Grondin said. Among them are likely to be staff members at the Barron Center, a long-term care and rehabilitation facility on Brighton Avenue that is owned by the city.

“We are working through that now,” Grondin said in an email, referring to the governor’s health care worker mandate.

Before Mills’ order, the hospital networks MaineHealth and Northern Light Health had already announced a requirement that their employees receive COVID-19 vaccines.

As the delta variant of COVID-19 sweeps the country and contributes to another surge in cases and hospitalizations, other states, such as California, New York and Washington, have also announced vaccine mandates for health workers. The details of each mandate differ, but in Maine, the policy will not include a religious or philosophical exemption, which means workers may opt out only for medical reasons.

Some places have gone even further. Last week, San Francisco announced that proof of vaccination would be required for those seeking to enter such indoor venues as bars, restaurants and gyms. That decree goes into effect Aug. 20.

Before that, New York City announced plans to mandate proof of vaccination for indoor dining, fitness clubs and other indoor activities. The city’s mandate will also apply to employees of those venues.

Across the country, more cities and towns are starting to impose vaccination mandates on public employees.

In June, San Francisco decided to require that city workers be vaccinated against the coronavirus once the vaccine receives full federal approval, a decision that could still be several weeks away. The three COVID-19 vaccines currently available in the U.S. are being dispensed under emergency authorization by the Food and Drug Administration.

San Francisco’s new policy, covering 35,000 municipal workers, may be the first by any city or county in the United States, according to The Associated Press. Once full FDA approval is given, municipal employees will have 10 weeks to get their shot. Those who refuse and don’t get an exemption could be fired. The policy applies only to city employees and does not include teachers, who are considered to be school district employees.

Last week, about 200 public employees in San Francisco wrote letters to the city’s Human Resources Department stating their opposition to the vaccine mandate. They claimed the city is attempting to infringe upon their “God-given and constitutionally secured” rights, according to the San Francisco Chronicle.

Last month in New York City, Mayor Bill de Blasio announced that all city workers would have to either get vaccinated or tested weekly for the coronavirus. Those who are unvaccinated must wear a mask when indoors at work, de Blasio said. If they refuse to wear a mask indoors, they will be terminated from their jobs.

And late last month, Eric Garcetti, the mayor of Los Angeles, announced that he will push for city employees to be required to be vaccinated once the vaccines receive full approval from the FDA.

The movement for public employees and health care workers to get vaccinated turned violent this weekend. The AP reported that a man was stabbed and a reporter attacked Saturday during a protest against vaccine mandates outside Los Angeles City Hall. Several hundred people holding American flags, Trump memorabilia and signs calling for medical freedom converged on the site, where they were met by a smaller group of counterprotesters.

Counterprotesters could be seen spraying mace while demonstrators at the anti-vaccine rally screamed death threats, the AP said.

Meanwhile, about 300 people opposed to Mills’ new COVID-19 vaccine mandate for health care workers protested peacefully Saturday on the Western Promenade in Portland, near Maine Medical Center. The protesters, many of whom were health care workers, called for personal choice in medical decisions, with some also spreading conspiracy theories and misinformation about vaccines and COVID-19. The Portland protest was organized by Mainers for Freedom.

Another group opposed to mandatory vaccines, Maine Stands Up, staged a protest – “Stand Up for Medical Freedom” – on Sunday at Broadway Park in Bangor. The group is planning another protest from 11 a.m. to 1 p.m. Tuesday at the State House in Augusta, according to a post on its Facebook page. It’s billed as a peaceful demonstration of constitutionally protected liberties.