In this Dec. 8, 2020, file photo, a health care worker wears personal protective equipment as she speaks to a patient at a mobile testing location for COVID-19 in Auburn. Credit: Robert F. Bukaty / AP

AUGUSTA, Maine — COVID-19 hospitalizations in Maine increased by 66 percent over the past week to their highest level since mid-May, with unvaccinated patients continuing to make up a wide majority of those admitted to hospitals.

The sharp rise reflects the wide reach of the virus within Maine with the spread of the highly contagious delta variant. As of Saturday, 123 people were hospitalized with COVID-19 here, according to the Maine Center for Disease Control and Prevention, up from just 74 a week prior and 25 a month ago. Nearly half of currently hospitalized patients are in critical care beds, while one-fifth are on a ventilator, according to state data.

Hospitalizations remain significantly lower than this past winter, when more than 200 patients were in the hospital with COVID-19. But the sharp upward trend now reflects how Maine’s high vaccination rate has been unable to hold off the spread of the delta variant, which now accounts for the vast majority of new cases in the region, according to the U.S. Centers for Disease Control and Prevention.

The increases were most notable at several hospitals serving more rural areas, while large hospitals in southern Maine did not see marked increases. At Northern Light Eastern Maine Medical Center in Bangor, 29 patients were hospitalized as of Monday, more than double the total a week prior and halfway to the hospital’s record high of 55 patients in January, according to Dr. James Jarvis, who helps lead Northern Light Health’s COVID-19 response. Waldo County General Hospital in Belfast had nine patients, compared with three a week ago.

Jarvis said the influx of patients at the Bangor hospital has caused officials to open a third intensive care unit for COVID-19 patients because the other two were at capacity. That number changes weekly but shows a concerning trend emerging with sicker patients, he said.

“We are open for full business right now, but this is taxing our system,” Jarvis said.

Patients hospitalized with COVID-19 continue to be mostly unvaccinated. Since the first Mainers became fully vaccinated, people who have not received the full vaccine course account for 95.9 percent of patients hospitalized with COVID-19, according to state data. About 64 percent of Mainers are fully vaccinated at this point.

High vaccination rates among nursing home residents and staff have largely limited virus transmission within long-term care facilities, once the source of many deadly outbreaks, but the virus is still spreading widely among Maine communities, with mask-wearing recommended in most Maine counties, according to the U.S. CDC.

BDN writer Caitlin Andrews contributed to this report.