The cases were among "folks who spent time in Provincetown" and some were breakthrough cases, people who tested positive for COVID-19 after receiving the vaccine, Morse said.
Breakthrough cases are rare -- 99.7% of new coronavirus cases in the U.S. are among people who have not been vaccinated, he said. But when an inoculated person gets the virus, the symptoms are much less severe.
The Health Department and Outer Cape Health Services are closely monitoring the situation in the Cape Cod town, Morse said.
"As always, we encourage people to make decisions that feel right for them," he said. "We have a lot of visitors in Town, and given the volume, it's inevitable that cases will continue to pop up over the summer."
He added that most year-round and part-time residents are fully vaccinated and reiterated that "the vaccine works."
More than 80% of adults in Massachusetts have gotten at least one dose of the vaccine and more than 4 million residents are fully vaccinated, according to state officials.
However, the Bay State is pushing for more people to get vaccinated as cases of the highly contagious delta variant sweep across Massachusetts. First identified in India and now in over 100 countries, the variant is approximately 60% more transmissible and could result in more severe disease. State officials estimate it will soon become the dominant strain.
Morse said he will provide updates on the Provincetown cases as more information becomes available.
The so-called Vax Bus is scheduled to stop in Provincetown on Thursday as the mobile coronavirus vaccination clinic works its way through Massachusetts.