Vaccine clinics for Island residents 65 and older and those with two or more underlying conditions began Monday after more than 1,200 appointments filled up in less than an hour Saturday morning, as a torrent of newly eligible Islanders rushed to schedule their shots for the week.

The online signup process Saturday and in-person clinic Monday appeared to run smoothly, according to firsthand accounts, social media and hospital officials — although all available appointments were taken by 8:50 a.m. Saturday, 50 minutes after bookings opened.

"We were so pleased with how the scheduling process went this morning," said hospital head of operations Claire Seguin in an email later Saturday morning. 

On Monday, the hospital moved through a steady stream of Islanders who had registered two days prior, vaccinating more than 150 newly-eligible residents. 

The online scheduling tool to set up an appointment went live on the Martha’s Vineyard Hospital Saturday morning. The process will repeat this coming Saturday at 8 a.m. Eligible Island residents can sign up for available vaccine appointments using an online tool on the vaccine page of the hospital website.

On Saturday at approximately 8:40, the hospital posted a Facebook update telling Islanders that if they got stuck with a “beating heart” loading page, to log out of Patient Gateway and sign back in. Patient Gateway is software used by Mass General-Brigham for patient signups.

Available appointments ran in 15 minute time slots from Monday, Feb. 22 through Saturday, Feb. 27. Hospital officials said they hoped to vaccinate 1,826 Islanders over the span of six days, including individuals receiving their second shot.

The hospital made made 1,235 total appointments available for the first dose of the vaccine. Another 591 appointments had already been scheduled for second dose vaccinations. 

Appointments on Nantucket, also available through the hospital’s portal, filled up before Vineyard slots — with no available appointments by 8:45 a.m. The Nantucket Cottage Hospital is also part of the Mass General-Brigham system.

The weekly appointment scheduling on Saturdays is driven by available supplies, Ms. Seguin said in an email Saturday after all the slots were filled.

"We are doing this, because we will not know until Friday of each week how many doses we will receive from the state. We are always dependent on the supply we receive from the state in determining the number of appointments we can schedule," she wrote. "We want to thank everyone for their continued patience during the vaccine rollout. Today was a good first step."

The second group of phase two of the state’s vaccine rollout is now eligible for shots, which includes those 65 or older, individuals with two or more underlying medical conditions, and individuals who live or work in public and private low income and affordable senior housing.

According to the state, qualifying medical conditions include asthma, cancer, chronic kidney disease, heart conditions, weakened immune systems from organ transplants, obesity, pregnancy, sickle-cell disease, smoking and type two diabetes. Individuals must be 18 or older.

When the new clinic began Monday, the hospital had already vaccinated more than 2,700 residents, including health care workers, first responders and individuals 75 or older, who were included in the first group of the governor’s phase two.

On Monday the opening day for vaccinations for people 65 and older was busy, with the hospital parking lots at capacity and orderly queues just inside the main entrance as people waited for their shots. Islanders chatted quietly at six-foot distances, some clutching their paperwork, while friendly hospital staff and volunteers handed out surgical masks, reminded people to clean their hands and directed them to the correct line.

Outdoors, cold rain fell beneath gray skies, turning the weekend snow to slush.

Vaccinations will continue every day this week.

The hospital will begin booking the next round of appointments on its website Saturday morning.

Updated to include reporting from the vaccination site Monday.