Citing urgent staffing and scheduling concerns, the Steamship Authority has sent a letter to the state Department of Public Health requesting guidance on the vaccination process for its 500 employees.

The issue of vaccinating SSA crew members arose at a Dukes County Commission meeting Wednesday afternoon, when Vineyard boat line governor James Malkin urged the county to send a letter to the state seeking assistance. SSA spokesman Sean Driscoll confirmed later that another letter had gone out that day from general manager Bob Davis.

In the letter to DPH commissioner Dr. Monica Bharel, Mr. Davis emphasized the boat line’s role as a lifeline to the Island and said that the pandemic had interrupted — and had the potential to further interrupt — ferry travel.

“Despite best efforts to educate our employees and the traveling public, the virus has sickened several of our employees, which has caused numerous disruptions to our operating schedules,” Mr. Davis wrote. “With the recent publicity concerning the availability and distribution of the Covid-19 vaccine to essential workers, we are requesting your attention to the need for the Authority to vaccinate our front line employees who interact directly with the traveling public and provide our vital service to the thousands of residents of Martha’s Vineyard and Nantucket.”

Although ferry interruptions have actually been rare, Mr. Driscoll said in an interview, the boat line had to cancel a pair of midday trips two weeks ago due to an employee testing positive for the virus. Earlier this summer three positive tests led to numerous ferry cancellations and schedule reshuffling.

On Friday the freight ferry Katama’s 6:30 p.m. trip out of Woods Hole was canceled due to unforeseen circumstances. Mr. Driscoll said a release would be forthcoming.

According to the state’s vaccination rollout plan, SSA crew qualify as front line transportation workers, putting them in the state’s second phase of vaccinations, which are set to begin in February. But phase two vaccinations run from February through April, making it unclear when the exact vaccination process would happen.

“There’s no doubt that we’ll be in the queue to be vaccinated,” Mr. Driscoll said. “But February or April? There’s a huge difference between those two days. We just don’t we don’t have any information at this point.”

Mr. Driscoll said the letter was mainly a request for guidance from the state.

“We’ve got 500 employees, who aren’t all geographically located in one place, who don’t all work every single day. So the logistics of how we are going to get the vaccine is going to take some working out,” Mr. Driscoll said. “How is it going to come to us? When is it going to come to us? It can’t just show up. We’re trying to get information to make sure we can do this in the most effective way possible.”

At the county commission meeting and in the letter, Mr. Malkin and Mr. Davis said increasing caseloads in the Cape and Islands region could threaten ferry service.

When an employee tests positive for the virus, all members of the crew have to stay home until they receive a negative test result, according to SSA policy. Mr. Malkin said 25 employees were at home as of Wednesday.

“Employee absences are increasing on a weekly basis and we are concerned that service restrictions and disruptions will become prevalent,” Mr. Davis wrote. “To avoid any long-term service disruptions or cancellations, the Authority seeks your attention and guidance on the best method(s) to obtain and coordinate distribution of the Covid-19 vaccine to our essential front line employees.”

The letter also said the SSA was available to assist the commonwealth in its vaccine distribution process.

A second letter went out Friday co-signed by the county commission and Nantucket selectmen.

SSA officials said they had not yet heard back from the state.

Aaron Wilson contributed reporting.