Covid-19 vaccine eligibility is set to open for all Islanders 16 and older this weekend, but the number of available appointments remains a moving target on the Vineyard, even as a more virulent strain of the virus has been detected and a recent surge in cases continues.

The long-awaited expansion in eligibility on Saturday, April 17, will include an estimated 8,000 Islanders younger than 55, according to 2019 Dukes County census data, doubling the number of residents eligible for the shot and opening the floodgates on what has already become a difficult appointment bottleneck.

The Martha’s Vineyard Hospital remains the only vaccination site on the Island and is dependent on receiving vaccine supply from the state. In an email this week, a hospital spokesman said there was no estimate for the number of vaccine appointments that would become available Saturday. The hospital has been scheduling vaccine appointments through a first-come, first-served online signup process.

The hospital receives its weekly, or 10-day, state vaccine allotment every Friday afternoon, and then opens vaccine appointments on Saturdays at 8 a.m. and Mondays at 5 p.m. For the past month, most of the doses have gone to second shots for high priority groups, although the number of first-dose shots expanded to approximately 1,000 this week, the hospital spokesman said.

Prior weeks had seen between 200 and 600 first-shot appointments become available.

According to state Department of Public Health data, approximately 44 per cent of the Dukes County population has received a first-dose, and 35 per cent has received a second dose. Only Barnstable County and Nantucket County have a higher percentage of residents who have received a first-dose shot.

But the signup process has been a struggle for some, prompting an unknown number of eligible Islanders to travel off-Island for their shots. Tisbury health agent Maura Valley said she received her second shot at a CVS in Falmouth earlier this week.

Meanwhile, a recent surge in cases on the Island continued this week, with health agents reporting 73 new patients between Sunday, April 4 and Saturday, April 10. Of the 73 new cases, 51 were tested at the hospital, 18 at TestMV and four at other providers. Health agents said 54 of the cases are symptomatic patients, 10 are asymptomatic, and 14 are unknown.

By Thursday, the Island had reported another 31 cases, making more than 150 in the past 14 days. Earlier in the week, the 14-day case count had reached close to 180 — the highest since the pandemic began.

The case surge comes as state epidemiologists confirm the presence of a more contagious virus variant on the Island. The B.1.1.7 variant, first identified in the United Kingdom, was detected in three of the six positive test samples sent to the state lab by the Island hospital and boards of health. Two of the samples came back inconclusive, and one was negative.

Later in the week, a hospital spokesman confirmed that the hospital would be sending off three or four samples from patients who had recently traveled to Brazil to test for the P.1 variant.

The UK variant, which officials said is more contagious than the original virus strain, has previously been identified in Cape Cod and Nantucket. There have been more than 1,000 cases of the variant identified in the commonwealth, according to the Center for Disease Control.

At a press briefing last Friday, hospital head of operations Claire Seguin said she had proactively asked the state to conduct testing for the variant after case numbers shot up last weekend. The hospital, boards of health and state DPH then worked together to choose cases that were determined to be high risk, Ms. Seguin said, settling on six to send to the state lab.

Ms. Seguin said she was not surprised by the results.

“I was actually suspicious of it [being here],” Ms. Seguin said, speaking of the variant. “But still, disheartened, and makes me [want to] double down on our protocols.”

The B.1.1.7 variant spreads faster and, in some studies, has been associated with sicker patients.

There are two patients currently hospitalized with the virus, according to an update from the hospital. As of Wednesday, both were in fair condition.

In a phone interview Thursday, Ms. Valley said she believed the presence of the B.1.1.7 variant accounted for a large part of the recent spread. Unlike the first case surge, which occurred in winter around the holidays, Ms. Valley said household contacts are almost always testing positive now.

“It’s just seeming more infectious,” the health agent said. “We saw it in cases like Shirley’s [hardware store in Vineyard Haven], where it pretty much went through the staff. And that’s what is really concerning. It is just apparently much more infectious, and it is lending itself to higher cases. And the number of younger people being infected has jumped.”

An expanded public health report issued last Friday for the Island showed a spike in the number of children under 10 and the number of people in their 30s who were being infected. While 33 per cent of the 1,170 positive Island cases have come in those two demographics, the number spiked to about 50 per cent this week, with 12 people under 10 and 23 in their 30s testing positive.

Ms. Valley said the connection was clear.

“People in their 30s are the ones with kids,” she said. “More household contacts are converting to positive now.”

She added:

“Younger people are the ones being infected . . . they are working in the trades, and they are the ones who haven’t been vaccinated yet.”

Ms. Valley continued to urge caution, saying that even as the vaccine becomes more widespread, mask use and social distancing remain as important as ever. A public health forum focused on vigilance and resources for Covid-positive patients was held Monday evening, with a second forum scheduled for April 28.

“We’re really trying to figure out our public outreach, with the summer season coming, and just let people know that we’re not done with this. Everything is still in place,” Ms. Valley said.

To schedule a vaccine appointment at the Martha’s Vineyard Hospital, go to during the designated times and click the ribbon at the top of the page that says “schedule your Covid-19 vaccine appointment.” Appointment time slots open online at 8 a.m. Saturday, and 5 p.m. Monday.