The Martha’s Vineyard Hospital’s smooth vaccine rollout took a sudden turn on Saturday, after the hospital received zero new Covid-19 vaccine doses from the state for the upcoming week, shutting out Islanders who had hoped to book appointments and sparking widespread frustration.

With no prior warning, a surprise statement on the hospital website at 8 a.m. Saturday said only 100 appointments could be booked for the coming week, due to the fact that no vaccine shipments had been received.

It marked the second week for booking appointments online for people 65 and over and those with two or more underlying conditions. Week one had seen 1,200 people vaccinated after a relatively smooth process for booking. Some 9,000 Islanders had gone online the prior Saturday, filling all available slots in less than an hour.

This Saturday was a different story.

After the morning kerfuffle, hospital called an impromptu press briefing at 11:30 a.m. to explain the surprise shortage, saying that the state had informed them of supply issues Friday evening but that the decision was made to wait until Saturday at 8 a.m. to make an announcement, with the hope that more vaccine would become available in the interim.

“This is what we know: DPH just told us it is the supply chain issue with the manufacturer,” hospital CEO Denise Schepici said. “Unfortunately as of 8 a.m. this morning, the state could not confirm any new doses.”

“This was a surprise,” she added.

Three days earlier hospital leaders had said in a briefing they were expecting to receive more than 2,000 vaccine doses from the state this week.

Ms. Schepici and head of operations Claire Seguin said they did not know when they would receive an update regarding the Island’s vaccine supply.

“We have stayed in contact with the state and now we have been told that we will receive a supply of vaccine at some point this week,” Ms. Schepici said Saturday. “How many doses, and when, is still not clear.”

The 100 appointments made available Saturday were due to excess supply, Ms. Schepici said. All those appointments were booked by 8:04 a.m., four minutes after the website had opened.

The problems sparked a flurry of comments on social media from Islanders who had waited eagerly for the past week to schedule their vaccine.

But on Saturday, hospital officials said the supply chain issues were not localized to the Vineyard and would affect vaccination sites statewide.

Hospital leaders defended their decision to not inform the public about what had happened before Saturday morning, saying they had been told by the state on Friday night to stand by.

“They asked us to stay tuned,” Ms. Seguin said. “They really worked with us and tried to get a confirmation to us sooner, but they were having their own supply chain issues,” she added.

Ms. Schepici concurred. “We could have easily gotten a number, and kept hoping that we would,” she said. “Rather than get everybody all upset needlessly, we were waiting until we had to go live.”

As for what happens next, Ms. Schepici and Ms. Seguin the hospital would make an announcement during the week if any more appointments become available, but a statement on the website said that would likely be “extremely limited.”

The next new vaccination bookings are planned for Saturday morning, March 6, according to the website.

And there could be other delays for the second shots. People who were previously scheduled to receive their second dose of the Pfizer vaccine will remain scheduled, Ms. Schepici and Ms. Seguin said. But the future was less clear for those who received the Moderna vaccine. Ms. Schepici said patients would receive an email from Patient Gateway — the hospital’s scheduling software — if their second vaccine dose needed to be rescheduled.

Ms. Seguin said a delayed second shot would not affect the effectiveness of the Moderna vaccine.

Ms. Schepici acknowledged the frustration. “We’re frustrated, the state’s frustrated . . . we know patients will be frustrated,” she said. “We doing everything we can to communicate what we know, when we know it.”

For those who were shut out Saturday morning, Ms. Schepici expressed deep sympathy, and said she wished she could give them a hug.

“I want to get everybody vaccinated,” she said. “We’re going to keep this going. We just, you know, we have to deal with our supply issues.”