The Maine State mobile COVID-19 vaccination unit is set up in the parking lot of the Oxford Casino, Monday, April 12, 2021 in Oxford, Maine. The clinic is set up in the parking lot of the Oxford Casino and will travel to other rural areas throughout the state. Credit: Andree Kehn / Sun Journal via AP

After months of waiting to get a coronavirus vaccine, Roger Knight was dismayed to wake up on Tuesday and learn the shot he got the day before was no longer being offered.

The South Portland ski shop worker had followed public health recommendations to get the first vaccine available to him, a single-shot Johnson & Johnson dose. He got his shot on Monday, and spent Tuesday with a headache and some fatigue — symptoms that are common after getting any of the three coronavirus vaccines.

The apprehension he felt was due to the news that the federal government was halting the use of the one-shot vaccine after six women between the ages of 18 and 48 among the millions to get the shot had developed rare blood clots in the days after their vaccinations.

Knight said he feels his chances of having a reaction like that are small. But he is still on “pins and needles” until more information is known about the occurrence.

“It would be a shame to shut down the vaccination process when it’s something we’ve all been waiting for,” Knight said. “But it’s also a tough spot to be in, when you wake up and hear the vaccine you just received is not being given out anymore.”

Those types of concerns are part of the challenge facing public health officials in Maine and the U.S. this week in the wake of the federal government’s cautious recommendation to pause vaccine’s use until the blood clots can be studied. Maine officials, looking to allay fears that might be raised by the pause, stressed the extreme rarity of the clots while couching the delay as a strictly cautionary and likely brief measure.

Maine announced it would be following the federal government’s recommendation early Tuesday morning. It set off a wave of cancellations as some providers scrambled to find doses to keep appointments open. The state’s mobile vaccination clinic had to solicit doses from providers to keep its clinic open Tuesday after canceling morning appointments.

Gov. Janet Mills said Tuesday the state is working on a public relations campaign with community leaders to drive home the importance of getting vaccinated, noting all three vaccines are virtually 100 percent effective in preventing severe cases of the virus.

Long odds of a severe reaction means there “should be no reason for hesitancy because of this blip,” she said at a press conference at which Nirav Shah, the director of the Maine Center for Disease Control and Prevention, was careful to note that the Pfizer and Moderna vaccines had not been linked to clots.

The public’s reaction to the vaccine news seemed to be mixed on Tuesday. While several people who answered a Bangor Daily News survey they were concerned about potential side effects, others said the risk seemed relatively small. Four out of five Mainers who had not received a vaccine last month said they planned to get one for the 10th-highest mark among states in a U.S. Census Bureau survey last month.

Annette Lease of Bangor got the Johnson & Johnson vaccine at Penobscot Community Health Care in late March. She said the experience was positive. While she had been open to getting any vaccine, she was “delighted to get the one-and-done” shot and not have to worry about finding time for a second appointment.

Lease said she was not worried about her own health upon learning about potential complications nearly three weeks after receiving her own dose. But she worried about others and wondered what the women who experienced blood clots might have in common.

Those questions will have to be handled delicately by public health officials to combat hesitancy, said Dr. Peter Millard, an epidemiologist who teaches at the University of New England, worked for the U.S. Centers for Disease Control and Prevention and practices as a physician at Seaport Community Health Center in Belfast.

He agreed with the decision to pause the vaccine’s use, saying officials would have risked appearing to not care about the clots and dinging trust. He said a “fair amount of people” were concerned about getting vaccinated prior to the pause and noted one of his patients expressed fears about the dose she received on a Tuesday visit.

Millard said it was likely the Johnson & Johnson vaccine would be limited to certain age ranges going forward, although the process is uncertain. That is what happened with the AstraZeneca vaccine in the United Kingdom, where a small number of people experienced similar clots.

In the meantime, officials should be diligent about explaining the nature of the pause and the side effects, Millard said.

“It’s better to err on the side of caution and have people think the public health authority is looking out for them,” he said. Otherwise, “even though it’s a small group, the message people are going to get is that the vaccine is unsafe.”

BDN writer Jessica Piper contributed to this report.