Vaccinations boost spirits at hospitals throughout Mass.

Previtera, who is 69 and lives in Westwood, was among the first of 119 people who received the new vaccine against COVID-19 at his hospital Wednesday, as the Massachusetts vaccination program got underway in earnest.

Health care workers at more than 15 other Massachusetts hospitals also received the shot, made by Pfizer and its German partner, BioNTech. Nearly 60,000 doses have arrived in the state. With a second vaccine made by Moderna likely to be authorized soon, the state expects a total of 300,000 doses by the end of the month.

But Previtera doesn’t plan to stop taking steps to prevent infection. “I won’t let my guard down. I don’t think any of us will,” he said. “COVID-19 is woven into the fiber of everyone’s life. It’s going to be part of our lives for some time.”

Even vaccinated health care workers will continue to wear full protective equipment at work because it’s not known whether the vaccine prevents the transmission of the disease. It’s possible that vaccinated people will pick it up without having symptoms and spread it to others.

The massive task of obtaining, storing, and administering the vaccine could not have come at a more difficult time, just as a second surge of COVID-19 is accelerating and straining hospitals. But for the very same reason, it could not have come at a better time, providing a figurative shot in the arm along with the real one.

“To see that box arrive and knowing that people are going to get vaccinated and there’s going to be an end to the pandemic is just inspiring,” said Peggy Stephan, the director of pharmacy at Beth Israel Deaconess. “It’s this symbol of — it’s finally going to end.”

The box Stephan was referring to arrived in a Ryder rental van early Wednesday afternoon, the hospital’s second shipment of vaccine. A white cardboard container about two feet high, it was ferried on a cart to the room with two freezers capable of storing at minus 94 degrees Fahrenheit.

Luca Cattaneo, specialty pharmacy manager, sliced the seal with a razor, lifted out a foil-wrapped ice pack, and then reached inside. Dry-ice steam billowed out of the box as if it contained a gift from aliens.

But the slender tray that emerged was purely the product of human ingenuity and labor. About an inch high and the length of a file folder, it contained 196 vials of the Pfizer-BioNTech vaccine. Each vial contains five doses, which will be diluted before being drawn into a syringe. The vaccine can survive five days in a refrigerator or six months in deep freeze.

The Beth Israel Lahey Health system, which encompasses 13 hospitals and 36,000 employees, has about 9,750 doses in hand. Nine of its sites started vaccinating Wednesday.

At least two hospitals, Tufts Medical Center in Boston and MetroWest Medical Center in Framingham, had administered first doses Tuesday, but the biggest push started Wednesday.

To prepare for the vaccination program, the staff at Beth Israel did several dry runs, with pretend patients, to make sure the process would flow smoothly, with appropriate distancing, said Stephan, the pharmacy director. Plans call for vaccination clinics seven days a week for the foreseeable future.

“We have an amazing team and they are putting in extra time,” she said. “They realize the importance and magnitude of what they’re doing.”

Employees who work directly with COVID-19 patients are first in line for vaccination. At Beth Israel, that includes those who work at COVID-19 testing sites, outpatient respiratory care areas, emergency departments, and urgent care centers.

In selecting employees to vaccinate first, the hospital included every type of staff person who works in a high-risk area, said Dr. Sharon Wright, infection control lead for the Beth Israel Lahey Health Incident Command. “Housekeeping, technicians, respiratory therapists — it doesn’t matter. Anyone who entered that space would get offered the vaccine at the same time,” she said. That would also include students and volunteers who work there.

The staff responded with “unbelievable excitement” when offered the vaccine, said Matthew Rabesa, executive director of employee health management at Beth Israel Lahey Health. Within 24 hours, they had booked appointments through the weekend.

Juan Cespedes was the first to receive the shot at Beth Israel on Wednesday. The 50-year-old Allston resident is an emergency department technician, who assists doctors and nurses with procedures.

He said he was “a little skeptical” about the vaccine at first, but decided it was best to get the protection. Moments after the injection, he said, “I feel more secure, more protected.”

But at work he will continue to wear protective equipment and doesn’t plan to let his guard down outside work either. “That would be irresponsible,” Cespedes said. “I can transmit it.”

Tyler Jensen, another emergency department technician who got vaccinated Wednesday at Beth Israel, has seen the toll of COVID-19 in his own family. His grandfather in Wisconsin died of the illness just last week.

Jensen, 23, said he had no qualms about taking the vaccine. “I have faith in the American health care system,” he said. “I was like, ‘Give me the shot as soon as you can.’ I feel very lucky and blessed.”

In emergency departments and intensive care units around the state, doctors and nurses as well as food, building, and environmental services workers also rolled up their sleeves Wednesday.

At Sturdy Memorial Hospital in Attleboro, employees pasted stickers on their scrubs reading “I received my COVID-19 vaccine” and posted photos on social media.

The first shots at St. Elizabeth’s Hospital were “very, very uplifting,” said Dr. Peter LaCamera, chief of pulmonary, critical care, and sleep medicine. But until the vaccines can be distributed on a mass scale, he said, “It’s going to be a very long winter from a COVID perspective. . . . Now is the time to double down or triple down on avoiding illness.”

Inoculations also started Wednesday at Massachusetts General Hospital and Brigham and Women’s Hospital in Boston, and North Shore Medical Center in Salem, with nine sister Mass General Brigham hospitals set to begin their injections Thursday.

“Our staff are acutely aware of the rising number of cases we’re seeing,” said Dr. Paul Biddinger, chief of emergency preparedness at Mass General. “They’re very hopeful about conquering COVID with this vaccine, but they’re desperately pleading with the public” to slow the virus spread by observing safety measures.

Robert Weisman of the Globe staff contributed to this report.

Felice J. Freyer can be reached at felice.freyer@globe.com. Follow her @felicejfreyer.