The U.S. government invested significant resources to ensure that as many Americans as possible could get vaccinated against COVID-19. With billions allocated to keep doses free, the vaccine was widely accessible throughout the country.

Despite the efforts, tens of millions of vaccine doses went unused.

According to a report the Centers for Disease Control and Prevention shared with NBC News, up to 82.1 million doses of COVID vaccines may have been discarded between December 2020 when vaccinations first began to mid-May 2022. The CDC noted that this figure would amount to about 11% of the overall vaccine supply to pharmacies to date that went unused.

Of the number of lost vaccinations, two companies accounted for a quarter of the losses: Wal-Mart and CVS. Between them, Walmart reportedly threw away about 10 million doses out of 44.6 million that it has received to date. CVS discarded about 11.8 million doses.

Other companies that reported wasted COVID vaccines include Health Mart, DaVita, Rite Aid, Publix and Costco.

The loss of so many COVID-19 vaccinations has been greeted with alarm by some experts, who lament that the doses could have been donated to poorer countries that continue to struggle with gaining access.

“It’s a tremendous loss to pandemic control — especially in the context of millions of people around the world who haven’t even been able to get a first dose,” Dr. Sheela Shenoi, an infectious disease expert at the Yale School of Medicine, told NBC News.

Previously, the CDC estimated that up to 65 million doses went to waste, according to a report by the Associated Press that cited CDC data. The latest figures are about 17 million doses higher than that estimate.

However, the companies accused of wasting the vaccines defend their actions by arguing that they provide vaccines on demand. They also point out that the two-dose nature of several of the vaccines leaves them with a short shelf-life by design that inevitably leads to wasted doses.

Others blamed patients for missing scheduled vaccine appointments and canceled visits, but said that they were working in line with CDC guidance that advises vaccinations to be prioritized even at the risk of wastage.

The CDC estimates that at least 82.8% of the eligible U.S. population has received at least one dose of a COVID-19 vaccine and about 77.9% have been fully vaccinated. These numbers are markedly lower for those that received booster shots with only about 46.9% of eligible Americans having received a third dose to date.