Virginia will require state workers to be vaccinated or get tested.

Virginia will soon require state employees to be vaccinated against the coronavirus or be tested every week, joining a few other states that have imposed similar mandates, Gov. Ralph Northam said on Thursday.

And Los Angeles County, the most populous county in the United States, will also require its employees to show proof of vaccination, beginning in the fall.

States, cities, employers and the federal government have all turned to mandates to accelerate the pace of vaccinations as cases have jumped across the country and the Delta variant has spread. Fully vaccinated people are protected against the worst outcomes of Covid-19, including those caused by the Delta variant.

New York, California and Puerto Rico have announced similar mandates, and last week President Biden said that federal employees would have to be vaccinated or regularly tested for the coronavirus. Major employers like Tyson Foods, Microsoft, ViacomCBS, Google and Disney have all instituted vaccine requirements of their own.

Virginia’s 122,000 state employees and contractors will need to be vaccinated by Sept. 1, or be tested every week, Mr. Northam said. Unvaccinated employees will also need to wear masks indoors and while conducting public business.

On Wednesday night, Hilda Solis, chair of the powerful Los Angeles County Board of Supervisors, announced that she was signing an executive order directing the county’s 110,000 employees to show proof of a coronavirus vaccination by Oct. 1. While exemptions will be made for medical and religious reasons, the executive order did not provide for a testing option as some other local governments have done.

Her authority to issue the regulation stems from Los Angeles County’s declaration of a local emergency in March 2020, the order said.

Ms. Solis said in a statement that since the city reopened on June 15 the average number of daily cases has shot up eighteen-fold and hospitalizations have gone up fivefold. “As vaccinations continue at a pace slower than what is necessary to slow the spread, the need for immediate action is great,” she said.

The spike in cases has been driven by unvaccinated residents, according to health officials.

At the same time, the city of Los Angeles and the state of California have issued mandates that ask government employees to get vaccinated, or agree to regular testing.

In Virginia, nearly 66 percent of adults are fully vaccinated, according to federal data, and the state has seen its daily average of coronavirus cases increase from a low of 129 on June 20 to 1,279 on Wednesday, according to a New York Times database.

“The arrival of the Delta variant, combined with the number of people who are not vaccinated, is driving our case counts back up,” Mr. Northam said at a news conference.

“The way that we’re going to win this war is to roll up our sleeve and get vaccinated,” he added.

Mr. Northam called for companies and local governments in Virginia to institute vaccine mandates of their own, and said he supported other mitigation measures, like masking, but that he was more focused on getting his state vaccinated than imposing a statewide mask mandate.

That approach is similar to that of Mayor Bill de Blasio of New York City, who called this week for proof of at least one vaccination before people can participate in indoor activities, like going inside a restaurant, gym or theater. He has strongly recommended that people wear masks indoors, but he has so far opted not to impose a mask mandate.

The Centers for Disease Control and Prevention last week recommended that even vaccinated people wear masks indoors in virus hot spots.

Mr. Northam said he had witnessed the ravages of fatal illness firsthand while working as a doctor.

“I have watched individuals fight for every breath, and I have also watched individuals take their last breath,” Mr. Northam said. “And so I want you to know that as your governor I will do everything that I can to keep you from that scenario.”