With COVID-19 vaccines having strict timelines for when they must be used before expiring, including some that must be used within hours of being mixed and thawed, having leftover doses may be somewhat inevitable.
So what happens in those cases? Who receives the doses and how do people find out where leftover shots are available?
Although there's no nation-wide data tracking wasted vaccine doses, it's likely that only a small fraction of distributed vaccine doses must be thrown away.
Still, this small fraction may amount to many thousands of doses -- and advocates say that it's crucial, in a time of limited supply and facing the specter of spreading variants, to get as many shots in arms as soon as possible.
According to a North Carolina Department of Health and Human Services (NCDHHS) report obtained by ABC station WTVD, 2,346 doses of the COVID-19 vaccine were marked unusable and thrown out in North Carolina.
And Texas issued a report on March 5 indicating that some 6,800 doses had been discarded out of 7.6 million -- about 0.09%. The state has administered some 6.7 million doses overall, according to its vaccination dashboard. Doses were discarded for a number of reasons, including that their expiration date had passed or inadequate refrigeration.
Some doses are wasted because of human error in mixing, preparation or transportation. But many doses are discarded when people don't show up to vaccine appointments, leaving extra shots on hand with a quickly dwindling expiration date.
Now, some local communities are crowdsourcing solutions. Some of those solutions are low-tech, like putting up a flyer at a grocery store notifying shoppers of extra vaccine doses.
Still, others rely on social media and the internet to give local residents a heads up about extra doses that would otherwise go to waste. Among those high-tech solutions are websites like Dr. B, VaccineHunter, and countless Facebook groups that have cropped up since the start of the vaccine rollout.