The vast majority of severe illnesses and deaths from the coronavirus in the Washington region are occurring among those who haven’t gotten vaccinated. And breakthrough cases of covid-19 among those who are inoculated are likely to be less severe and not require hospitalization.

In Maryland, unvaccinated people make up about 96 percent of covid-19 infections, hospitalizations and deaths, according to state data.

The same is true in Virginia, where 99 percent of covid-19 infections, 97 percent of hospitalizations and 98 percent of deaths are occurring among the unvaccinated, according to state data.

In D.C., where 55 percent of residents are fully vaccinated, there have been 546 cases among about 299,000 vaccinated people. Of that number, 39 were hospitalized and four died, city data show.

Meanwhile, the spread of the virus in D.C., Maryland and Virginia has risen steadily in the two weeks since the Centers for Disease Control and Prevention recommended that people in communities with high and substantial community transmission resume wearing masks indoors, regardless of vaccination status.

According to the CDC, Virginia has an overall high rate of community transmission, with about 137 cases per 100,000 people in the last seven days.

Of the 133 counties and cities in Virginia, 97 have high transmission and 28 have substantial transmission, while five have moderate transmission and just three — the cities of Fairfax and Manassas Park plus Bath County — have low transmission.

D.C. has high community transmission, with about 123 cases per 100,000 people in the last seven days, CDC data shows.

Mayor Muriel E. Bowser (D) recently reimposed an indoor mask mandate for everyone, vaccinated or not, in response to the increasing numbers.

More than half of Maryland counties have substantial transmission of the virus, including Montgomery County, while seven have high transmission, including Prince George’s County, a majority-Black county that has had some of the highest covid-19 death rates in the region.

Hospitalizations across the region are nowhere near the peak reached this spring, but the number of people being admitted with covid-19 is on the rise.

The seven-day average of covid-19 hospitalizations was 763 in Virginia on Wednesday, the highest it’s been since early May, while that number was 583 in Maryland — the highest since late May. In D.C., the seven-day average of covid-19 hospitalizations was 78, a number that has crept up after a lull beginning in late June.

The Inova Health System, which operates Fairfax Hospital, had about 50 covid-19 inpatients Tuesday — far below the 450 it had in late April and early May, but the number is rising, said Steve Motew, a physician and chief of clinical enterprise for Inova.

“We are seeing for sure much lower volume than any other time or surges in general. It’s not zero, however, and it has been slowly increasing,” Motew said in an interview.

“We’re clearly in the next wave. If you look nationally this looks to be our fourth wave,” said Neil J. Sehgal, an assistant professor of health policy and management at the University of Maryland School of Public Health. “The concern is the wave in magnitude of cases will match our winter wave, the last big wave we saw.”

Virginia, Maryland and D.C. are not experiencing infection rates as high as places like Florida and Texas, where the vaccination rate is generally lower, but considering the national picture, Sehgal said, it’s too early to say the virus has peaked locally.

Public health experts say fear of the highly contagious delta variant, which is responsible for most new cases, is prompting some who were previously skeptical or apathetic about the vaccine to get inoculated.

Danny Avula, Virginia’s vaccine coordinator, said more Virginians are getting vaccinated. The state hit a low point of about 11,000 doses a day last month but is now above 14,000 doses, state data shows.

“The reality is it is the impact of delta and it is a more contagious disease,” Avula said in a call with reporters Tuesday. “It causes cases to surge, hospitalizations to surge across the country. It has put vaccination back on the radar for many Virginians.”

That is especially true with school starting up again, he said, given than children under 12 are not yet eligible to receive the vaccines.

“The bulk of our population will likely be exposed to the delta variant in the next few months,” Avula said. “And they’re either going to be exposed vaccinated or unvaccinated.”

Virginia is planning to change the way it reports breakthrough cases to provide more context to the numbers, comparing the rates of infection between people who are vaccinated and people who are not vaccinated, said Lilian Peake, the state epidemiologist.

“Looking at the proportion of new cases that were not vaccinated over time does not provide an accurate picture of whether or not the vaccines are effective,” Peake said in a statement Wednesday. “This is particularly true while the level of vaccine coverage is increasing and new cases are surging.”

There had been 5,139 breakthrough cases in Maryland as of Sunday, of about 3.3 million people vaccinated; of that number, 519 were hospitalized and 61 died.

In Virginia, there had been 3,359 breakthrough cases as of Friday, representing less than one-tenth of 1 percent of the more than 4.6 million vaccinated people in the state. Of that number, 218 were hospitalized and 50 died.

Public health experts note that the coronavirus will not go away after the delta surge ebbs.

“We have the point of view that the enemy is the virus and the longer the virus circulates in the community the better the chance it will mutate again,” Motew said.

William Petri, an infectious-disease specialist at UVA Health, said more than 80 percent of people admitted to the hospital with covid-19 have the delta strain. He was especially worried about the immunocompromised and solid-organ transplant recipients.

Like many vaccinated people, Petri said he felt comfortable a few weeks ago removing his mask at his local coffee shop, but as the numbers ticked up and CDC guidance changed, he donned the mask again.

He had been hoping the worst of the pandemic was over — but his optimism was short-lived.

“Everything I thought was going to happen with the pandemic has been wrong,” he said.