At least 15 million COVID-19 vaccine doses in the U.S. have been thrown away since March, a new report finds.

The government data obtained by NBC News revealed that pharmacies and state governments wasted far more doses than initially known. Of the wasted vaccines, some were due to cracked vials and diluting errors while others were due to vials having more doses than people who wanted them.

Sharifah Sekalala, an associate professor of global health law at England's University of Warwick, told NBC News that it is “really tragic that we have a situation where vaccines are being wasted” while other countries are facing vaccine shortages.

"A lot of the global south is unvaccinated. The African continent is still below 10 percent, and that's just a huge inequality and it's really problematic," Sekalala said.

NBC’s findings show almost double the number of wasted vaccines that was initially reported by the Centers for Disease Control and Prevention on Tuesday. The CDC data revealed that Walgreens wasted almost 2.6 million doses while CVS, Walmart and Rite Aid wasted 2,3 million, 1.6 million and 1.1 million doses respectively.

The CDC data is self-reported by pharmacies and government agencies and it does not include all vaccine providers.

However, total wasted Covid vaccines “remains extremely low, which is evidence of the strong partnership among the federal government, jurisdictions, and vaccine providers to get as many people vaccinated as possible while reducing vaccine wastage across the system,” CDC spokesperson Kristen Nordlund said in an email.

Walgreens spokesperson Kris Lathan told Kaiser Health News in May that "our goal has always been ensuring every dose of vaccine is used."

Health officials are recommending people to get vaccinated as soon as possible, as high vaccine demand correlates with less wasted doses.

As of Tuesday, just over 205 million people in the U.S. have received at least one dose of a COVID-19 vaccine and about 175 million people are fully vaccinated, according to the CDC.