Data from These 4 Studies Convinced the CDC to Let Vaccinated People Ditch Their Masks

In a surprising move after months of caution, the Centers for Disease Control announced Thursday that they were recommending lifting mask requirements for fully vaccinated people in most indoor and outdoor settings, regardless of social distancing.

The decision was a significant shift towards normalcy in the U.S. after nearly 15 months of the COVID-19 pandemic, and one the federal health agency said was prompted by the increasing number of vaccinations, declining COVID-19 cases and new research on the efficacy of the vaccines.

"Numerous reports in the literature" provided real-world data that fully vaccinated people are highly protected against the virus, CDC Director Dr. Rochelle Walensky said during the announcement.

RELATED: Vaccinated Americans Can Now Go Without Masks in Most Indoor and Outdoor Places, CDC Says

Jeff Gritchen/MediaNews Group/Orange County Register via Getty People dine indoors during the COVID-19 pandemic

Walensky first pointed to a study of 6,700 health care workers in Israel who had received Pfizer's COVID-19 vaccine. The study, published May 6 in the Journal of the American Medical Association, found that vaccine was 97% effective in preventing symptomatic cases of COVID-19 and 86% effective at stopping asymptomatic infections.

Walensky also referenced two recent studies from the CDC. The first, from late March, determined that both Pfizer and Moderna's vaccines are "highly effective" at reducing the risk of infection from COVID-19, after monitoring 4,000 health care workers, police, firefighters and other essential workers for four months.

The report found that the risk of infection went down by 90% two weeks or more after they received their second dose, and even one dose alone provided significant protection, around 80%, two weeks after their first inoculation.

RELATED: Large Study Confirms COVID Vaccines Are Working in the U.S., Reducing Risk of Infection by 90%

The other CDC study looked at people 65 and older who had been fully vaccinated, and found that Pfizer and Moderna's vaccines were 94% effective in preventing hospitalizations for COVID-19.

The final study Walensky highlighted was about the effectiveness of Pfizer's vaccine against two strains of COVID-19 — the B.1.1.7 variant first found in the U.K., and the B.1.351 variant that moved through South Africa. The vaccine prevented 89.5% of cases of the B.1.1.7 variant, and 75% of the B.1.351.

"The science is clear: If you are fully vaccinated, you are protected, and you can start doing the things that you stopped doing because of the pandemic," the CDC said in a statement on Thursday.

Listen below to the episode of our daily podcast PEOPLE Every Day for more on the new CDC guidelines.

Officials are hoping that lifting mask restrictions will encourage more Americans to get vaccinated as the rate of inoculations slows. As of May 14, just under half of the U.S. population, 46.6%, have received at least one dose of a COVID-19 vaccine, and 35.8% are fully vaccinated, according to the CDC. But the number of daily vaccinations has dropped from a peak of more than 3 million shots a day on average to just over 2 million in the last month.

New COVID-19 cases, though, are sharply declining as more people get vaccinated. As of May 14, the U.S. is seeing an average of around 36,000 new cases a day, a 30% decrease in the last two weeks, according to The New York Times.

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