The largest union of registered nurses in the United States has publicly condemned the Centers for Disease Control and Prevention over the weekend for ditching most mask recommendations for those who have been fully vaccinated, The New York Times reports.

National Nurses United (NNU) called out the decision to allow fully vaccinated Americans to go almost anywhere without a mask as "not based on science" and urged the CDC to roll back the recommendation.

As of right now, many major retailers around the country are no longer requiring shoppers to wear masks. In other words, they are counting on those to have not been fully vaccinated to still wear a mask without any form of verification — meaning that, inevitably, some unvaccinated people are also forgoing masks in public.

The union's executive director Bonnie Castillo said in a statement that the CDC's decision was "a huge blow to our efforts at confronting this virus and the pandemic" and that masks are "another lifesaving layer of protection for workers."

Less than half of the country has received a single dose of the COVID-19 vaccine. Fewer than 40 percent are fully vaccinated.

In addition, questions about the effectiveness of vaccines remain. We still don't fully understand if vaccines are able to completely stop asymptomatic infections or how long immunity lasts.

We also don't know how future variants of the coronavirus will affect the effectiveness of currently available vaccines.

The new guidelines, the NNU said, "will disproportionately harm Black, Indigenous, and people of color."

"There has been so much inequity in the vaccine rollout and racial inequity in who is a frontline worker put most at risk by this guidance," said NNU President Zenei Triunfo-Cortez in the statement. "The impact of the CDC’s guidance update will be felt disproportionately by workers of color and their families and communities."

The CDC announced last Thursday that it's advising Americans who are fully vaccinated — two weeks past the second shot of either Pfizer or Moderna, or the first of Johnson & Johnson's vaccine — that they can stop wearing masks or maintain social distance in most settings.

The agency caught government officials, worker representatives, and businesses by surprise.

"While we all share the desire to return to a mask-free normal, today’s CDC guidance is confusing and fails to consider how it will impact essential workers who face frequent exposure to individuals who are not vaccinated and refuse to wear masks," Marc Perrone, the president of the United Food and Commercial Workers union, told the NYT last week.

CDC director Rochelle Walensky defended the decision on Sunday, telling NBC that "we are asking people to be honest with themselves. If they are vaccinated and they are not wearing a mask, they are safe. If they are not vaccinated and they are not wearing a mask, they are not safe."

The pandemic is far from over. Hundreds of Americans are still dying from the deadly virus every single day.

"Now is not the time to relax protective measures, and we are outraged that the CDC has done just that while we are still in the midst of the deadliest pandemic in a century," Castillo said in the statement.