As Massachusetts vaccination sites ramp up the number of people receiving the COVID-19 vaccine, what happens to unused doses is drawing increasing scrutiny from the state, as well as from members of the public eager to snatch up any leftovers.

The vaccination site at the DoubleTree Hotel in Danvers became chaotic Wednesday after word spread on social media that there were extra doses available. People lined up outside and waited for hours, and some under age 75 were able to get vaccinated.

In a written statement, Curative, the company running the vaccine site, said additional appointments were available because of cancellations earlier in the week due to the snowy weather.

“To avoid doses going to waste, Curative offered patients who were already registered with appointments later in the week to come to the Danvers location to receive their dose,” the statement said. The statement did not address the fact that many of those who showed up did not have appointments and did not meet the state’s age requirement.

"We have policies in place with respect to dosing and eligibility standards and we expect those to be adhered to,” Gov. Baker said, when asked the following day about the Danvers situation. “And we don't believe that there should be sort of a cattle call at the end of the day. People need to manage their dosing and manage their vaccine, and we expect all the sides to do that going forward.”

Baker stressed that the way to get vaccinated is for eligible people to make an appointment using the state’s registration website or by calling 211.

Despite the policies Baker emphasized to prevent wasted doses, a public information request from the Boston Herald revealed this week that more than 1,200 doses have been wasted in Massachusetts so far. And that doesn’t include almost 2,000 doses that went bad at a VA Hospital in Jamaica Plain when a freezer broke.

When asked about that Herald report, Baker noted that the rate of wasted doses is low, considering the huge volume being processed in the state.

“At this point, we're talking about an unused rate of 0.13 percent,” Baker said. “In my view, any dose you lose is a problem. But that's a pretty small number in the grand scheme of things."

Managing doses so none go unused is a complicated process.

The Moderna vaccine comes in packages of 10 vials, and each vial contains 10 doses, although sometimes those administering the vaccine are able get an eleventh dose out of a vial. There are five Pfizer doses in a vial, although distribution sites can often stretch that to six.

But stretching the doses can complicate things, because sites then have to make sure they can get that same number from vials again four weeks later when people come in for their second shot.

And for both the Moderna and Pfizer vaccines, once a vial is punctured, its doses must be administered within six hours. So the staff running vaccination clinics need to carefully ensure that enough vaccine is available for everyone with an appointment, while also making sure they don’t open vials that can’t be fully used.

Because the Pfizer vaccine requires extremely cold storage, even unopened vials must be used within five days of being defrosted. Timothy McDonald, director of health and human services for Needham said when necessary, they’ve set up smaller clinics to use up defrosted vials.

“We basically went to our senior center and [said], 'Oh, you've gotten a lot of inquiries. Who have you got inquiries from? Let's start calling them. Let's see if they want to come in,'" he said.

On Friday, CIC Health, which is running mass vaccination sites for the state, reported hitting a milestone of 50,000 vaccinations at Gillette Stadium. Five thousand people have been vaccinated at Fenway Park so far. Rodrigo Martinez, the company’s chief marketing and experience officer, said no doses have been wasted at either site. As each day draws to a close, he said, they continually check to see how much they need to prepare.

"The protocol is first slow down the number of vials that you open, so you try to approach as much as possible the number of people [needing to be] vaccinated,” Martinez said. “And, by the way, there are several days over the last few weeks where we end up with zero extra doses. It just matches perfectly."

When they do have a few leftover doses at the end of the day, Martinez said, they’re given to people working at the site who have not been vaccinated.

"Every day we have a couple of people that come to the sites, to Fenway or Gillette, and they're like, ‘Hey, what do you do with extra doses?’ And we just explain, ‘This is the protocol. We're not going to have any extra for you right now out here in the street.’"

Despite the thousands of doses given at the mass vaccination sites, Martinez said, people are more likely to find an unused dose at a pharmacy. Although in an email to GBH News, a spokesperson for CVS said that’s not their policy.

“If one of our long-term care facility vaccination teams is onsite and cannot use all doses requested by the facility, our team determines if the remaining doses will remain clinically viable and can be transported for use at another facility or for another eligible population,” the CVS spokesperson said. “In the rare instance that doses have reached their expiration they are disposed of per CDC and manufacturer guidelines.”

On Thursday, the state instructed hospitals that were running vaccine clinics to stop making new first-dose appointments in order for those doses to be redirected towards the mass vaccination sites.

“Personally, it’s disappointing,” said Dr. Karl Leskowksi, associate chief medical officer for Brigham and Women’s Hospital. But, he said, if it turns out that the new strategy ultimately means more people are vaccinated quickly and equitably, he’d support it.

Leskowski said until now, when there have been leftover shots available at the end of the day, they’ve been able to give them to unvaccinated patients in the hospital. But it’s not clear what will happen moving forward.

"In three weeks, when we're in the last week of our second doses, if we have an extra dose, who do we give it to and how do we ensure that they will have access to their second dose if it's not on our campus?” Leskowski asked. “I think we have a little work to do with the state to clarify, how do we make sure that they are taken care of?"