Five Martha’s Vineyard Hospital staff who had received vaccination shots have tested positive for coronavirus after being exposed to a Covid-19 positive patient and other positive staff, hospital officials confirmed on Friday afternoon.

In an impromptu press briefing, hospital CEO Denise Schepici and head nurse Claire Seguin said the patient had tested negative when admitted to the hospital on Monday for a non-Covid related illness. Per hospital protocol, the patient was retested for the virus 72 hours later on Wednesday, and came back with a positive result.

Three of the staff members who were in contact with the patient tested positive yesterday. The other two staff members who tested positive did not have contact with the patient but work in the hospital, likely contracting the virus through community spread, according to officials. Those staffers started showing symptoms yesterday, Ms. Schepici said.

She did not specify what jobs the staffers work at the hospital.

Although contact tracing is still underway, no other hospital patients were exposed to the Covid-positive staff, Ms. Schepici and Ms. Seguin said. They emphasized that the hospital remains safe for patients, even with the prevalence of the virus throughout the community.

“This virus is very much with us on the Island,” Ms. Schepici said.

In their daily case report Friday, Island health agents classified the hospital cases as a cluster.

All the Covid-positive hospital staff have received at least one dose of the vaccine, according to Ms. Schepici. Four of the five staffers had received both doses.

According to hospital officials, the vaccine is not immediately effective after the shot is administered, often taking approximately two weeks to create immunity to the virus. The hospital staff who tested positive had not completed the full-two week period after their second shots.

“They were still in their window,” Ms. Seguin said.

“This is a good reminder about the vaccine,” Ms. Schepici added. “It depends on the individual as to when the vaccine becomes fully effective. A person who has been given the vaccine may no longer be at risk for the effects of the virus, but that person can still be a carrier of the virus.”

The Covid-positive staffers are currently in good condition in quarantine, Ms. Schepici and Ms. Seguin said. There are 20 hospital employees who have been tested for the virus, with 12 tests coming back negative and eight still pending.

“We are confident that the situation was contained to our immediate steps of tracing, testing, and sanitizing the hospital on a continual basis,” Ms. Schepici said. “All staff members who came into contact with our employees have been notified, and are being tested.”

The hospital has slightly different PPE requirements for Covid-positive and non-Covid patients, according to officials. Responding to questions regarding the safety protocol of hospital employees, Ms. Schepici and Ms. Seguin said they did not believe staff violated any procedure regarding sanitization and PPE wearing in treating the patient, and that they would not require stricter PPE for staff treating non-Covid positive patients.

“I do believe the staff were all adequately dressed in PPE, at least the three that were exposed to the patient,” Ms. Schepici said. “The other two were just pure community spread . . . I think that what this speaks to is just how virulent it is. Despite all of our precautions, exposures can happen.”

Hospital staff confirmed in the spring of 2020 that an employee had tested positive for the virus after exposure in the hospital. It is not clear whether other hospital staff have tested positive in the time since. Ms. Seguin also said that this is not the first routine patient to test positive for Covid-19 after admission.

Asked about the timeline of the Covid-19 patient’s infection, Ms. Schepici and Ms. Seguin said they believed it had occurred before the patient was admitted to the hospital, rather than after.

“We’re still looking into that,” Ms. Seguin said. “But looking at the timeline, it appears that that patient was likely already infected, and it wasn’t until a few days into the admission, that they actually turned to positive.”

Ms. Schepici assured that the hospital remains safe, with staff taking all precautions to protect their patients.

“Our hospital is safe,” Ms. Schepici said. “We have strict cleaning procedures. We screen our patients for their safety, and for our employees. We wear masks. We use PPE when caring for Covid patients, and practice safe hygiene and social distancing.”

Meanwhile, hospital officials said that they had jump-started phase two of the vaccination process on the Island, with clinics planned for residents over 75.

The hospital received 200 additional doses of the vaccine late this week, according to Ms. Schepici, providing them with 570 shots for the community.

“We communicate with the state daily, and we feel they understand our needs as a hard-to-reach rural community,” Ms. Schepici said.

The first clinic will take place on Monday, Feb. 1, with other clinics scheduled for Wednesday, Thursday and Friday from 8 a.m. to 4 p.m. The hospital is contacting patients who qualify for the vaccine through its Patient Gateway system. Residents who do not use Patient Gateway can fill out a vaccine attestation form on the state Department of Public Health website, and forward the confirmation form to mvhinnovations@partners.org.

“We have a vaccine clinic on Monday. I want our community to know that we are ready,” Ms. Schepici said. “We will, as we always do, take all precautions to keep you safe while you get your vaccine.”