Over 82 million doses of COVID-19 vaccines distributed across the country have gone to waste since the start of the pandemic, according to data from the Centers for Disease Control and Prevention.

Why it matters: Vaccine waste has been an ongoing concern during the pandemic that has highlighted worries about the efficacy of the vaccine rollout.

• The latest figures represent a large spike since late February, when roughly 65 million doses were estimated to have been wasted, per AP.

The big picture: The new 82 million estimate means that between December 2020 and mid-May, slightly more than 11% of the doses distributed by the federal government were thrown away, NBC News reported.

• CVS and Walmart, two pharmacy chains that have worked to administer COVID-19 vaccines, were together responsible for more than 25% of the doses that went to waste.
• Other pharmacies — including Rite Aid and Costco — and dialysis centers each wasted more than a quarter of the doses they received, per NBC News.
• Among states, Oklahoma discarded about 28% of the doses it received, while Alaska threw away nearly 27% of its doses.

State of play: The vaccine comes in vials with multiple doses, but their short shelf life means that once a vial is opened, if it isn't used up quickly, it will have to be thrown away.

• The World Health Organization estimates that large vaccination campaigns using multidose vials will see significant rates of waste.
• Less than half of fully vaccinated adults in the U.S. have received their first booster shot, per CDC data.