Nearly 2,000 doses of Moderna's coronavirus vaccine were destroyed on 19 January after a cleaner at Boston University's Jamaica Plain Campus accidentally unplugged a freezer were they were being stored.
"As a result, 1,900 doses of the Moderna Covid-19 Vaccine stored in the freezer were compromised," Kyle Toto, public affairs specialist at VA Boston Healthcare System, said, as quoted by ABC News.
He added that the freezer had an alarm system installed and an investigation into why it failed is now underway.
However, the accident is not expected to affect the US government's inoculation programme as "replenishment doses are in process," Toto added.
According to the Centres for Disease Control and Prevention, the Moderna vaccine is kept at temperatures between -13 and 5 degrees Fahrenheit. After that, they can be kept frozen or stored in a fridge between 36 and 46 degrees Fahrenheit for up to 30 days before the vials are opened.