Health officials on the Island are conducting contact tracing this week after a reported case of chickenpox at the Martha’s Vineyard Public Charter School.

Martha’s Vineyard Hospital reported Friday that two additional cases are also being investigated after the first case from earlier this week.

“We are working in collaboration with the board of health and the school on a solution to address potential exposure to students,” said Claire Seguin, the hospital chief nurse and the vice president of operations.

Parents will be notified if their children were exposed to the disease, which can be serious for both children and adults.

According to the hospital, studies have shown that chickenpox-related hospitalizations have decreased since the vaccine became available in 1995.

The Island schools have some of the lowest vaccination rates in Massachusetts, according to data recently released by the state Department of Public Health.

While the Chilmark school kindergarten has the second highest vaccine exemption rate of any school in the state, the charter school kindergarten also had a high rate of 12.9 per cent.

In a letter Thursday, charter school director Peter Steedman alerted parents to the recent case, and, after consulting with the state Department of Public Health and Island officials, said children should be vaccinated as soon as possible if they haven't had the illness previously.

Chickenpox causes an itchy rash that usually lasts about a week. Cases are often mild but can be serious in infants, adolescents, adults, pregnant people, and people with a weakened immune system.

Most people who have been vaccinated with two doses of the chickenpox vaccine are protected for life, according to the hospital.

The best way to avoid the disease is getting vaccinated, said Ms. Seguin.

“Vaccines help bring the spread of chickenpox, and other infectious diseases, under control,” said Ms. Seguin. “Low vaccination rates introduce a vulnerability.”