Published in the February 18, 2021 edition.

BOSTON — As about 1 million more people became eligible for the COVID-19 vaccine Thursday morning, the state-run website that people must use to find and book most appointments has crashed and does not appear to allow residents to schedule vaccinations.

The state’s COVID-19 Command Center was not immediately available to provide details, but people visiting the website after 8 a.m. Thursday were met with a message that “this application crashed.” Visitors were advised to try again later.

“Due to high volume, is currently experiencing technical difficulties. Appointments at mass vaccination locations have not yet been posted today, but will be made available soon. More updates to follow,” the official state government Twitter account posted around 8:45 a.m.

When Gov. Charlie Baker announced Wednesday that people 65 years old or older, the residents and staff of affordable and low-income housing for seniors, and people with two or more health conditions that put them at higher risk for hospitalization or death would be able to start booking vaccination appointments at 8 a.m. Thursday, it represented a doubling of the number of people currently eligible for the limited number of vaccine doses.

The interest was immediate. When word of the governor’s announcement got out before his press conference, the website saw about 250,000 visits.

Baker said Wednesday that he thinks the vaccination appointment website “will be in good shape” for the added traffic Thursday morning.

The governor’s Thursday schedule did not include a press conference or any event at which he might face live questions from reporters when his office released it at 8 a.m., though he is slated to address the Greater Boston Chamber of Commerce virtually at 10 a.m.

Yesterday, state officials announced that people age 65 and older, residents and staff of low-income and affordable senior housing, and individuals with two or more health conditions that put them at higher risk from COVID-19 will be able to start booking vaccine appointments Thursday, as the state shifts to the next priority group in its phased immunization plan.

The expansion of eligibility to a population of roughly 1 million new people comes as the Baker administration is also pursuing what officials describe as a streamlining of its vaccination program to focus on high-capacity sites.

The administration sent a letter Wednesday to local boards of health informing them that starting March 1 the state will no longer provide first doses to municipalities running individual vaccine clinics that only serve their own residents. The 68 current municipal clinics will receive second doses so that they can fully vaccinate people who have gotten the first shot, Health and Human Services Secretary Marylou Sudders said in a briefing.

Twenty communities the Baker administration identified on Tuesday as disproportionately impacted by COVID-19 will remain eligible to receive and distribute vaccine at the local level, Sudders said.

The goal, Sudders said, is to increase capacity at locations like mass vaccination sites, regional collaboratives and pharmacies, and to have a uniform set of rules across the different sites, rather than have some only serving residents of a particular community.

Ninety-five percent of people in Massachusetts live within a 45-minute drive of a mass vaccination site or within 30 minutes of one of 13 regional collaboratives, Sudders said. Critics of the vaccine distribution effort in Massachusetts have raised concerns about how people will access the large-scale vaccine sites if they cannot drive or do not have someone to transport them.

The companion policy that allows otherwise-ineligible people to get their shot if they accompany someone age 75 and older to a mass vaccination site will continue to apply only for that age group.

More than 50 percent of the 75-plus population has so far been vaccinated, Sudders said, a threshold that made state officials comfortable adding new eligibility groups.

Because of supply constraints, it could take more than a month for all eligible groups to secure a vaccine appointment, Sudders said. She said the state received word late Tuesday night that its supply from the federal government would increase to 139,000 first doses a week, from about 110,000 first doses.