Washington DC - The Centers for Disease Control and Prevention recommended on Tuesday that some people vaccinated against Covid-19 should resume wearing face masks indoors due to the alarming spread of the Delta variant.

White House spokesperson Jen Psaki said on Tuesday that the change on mask guidance is due to evolving data on the highly contagious variant.

She emphasized that the three currently authorized Covid-19 vaccines provide ample protection against the virus, but wearing a mask can help prevent its spread and save lives.

"The reality is we are dealing with a much different strain of the virus than we were earlier in the spring," Psaki said.

The new guidelines apply to vaccinated individuals who live in areas of the country where Covid-19 transmission remains high.

"To maximize protection from the Delta variant and prevent possibly spreading it to others, wear a mask indoors in public if you are in an area of substantial or high transmission," the revised CDC website said.

"Wearing a mask is most important if you have a weakened immune system or if, because of your age or an underlying medical condition, you are at increased risk for severe disease," it added.

The CDC made the decision after considering new data. National Institutes of Allergy and Infectious Diseases director Anthony Fauci briefed President Joe Biden on the change early on Tuesday.

The Delta variant has caused an uptick in Covid-19 cases in recent weeks among the unvaccinated, leading many public health experts to fear an even greater spike in cases in the coming weeks and months.

In May, the CDC said fully vaccinated Americans could ditch masks indoors due to low transmission rates across the country and high rates of vaccinations.

But in recent weeks, vaccinations have plateaued, and just 60% of American adults are fully vaccinated. Polling indicates getting the remaining 40% across the finish line could be a slow crawl, as many unvaccinated Americans say they are not interested in getting a shot.

Meanwhile, Covid-19 vaccines are only allowed for children aged 12 and up. Earlier this month, the CDC said all fully vaccinated school-age children could go maskless in the classroom, and unvaccinated students should mask up.

Soon after the agency released the guidance, the American Academy of Pediatrics recommended all students, regardless of vaccination status, mask up in the classroom to help prevent transmission.

Although children are less likely to be hospitalized or die as a result of Covid-19 compared to adults, physicians warn children can still suffer from the long-term effects of the disease for months after recovery.

Also, the rapid spread of Covid-19 among unvaccinated children could lead to the creation of new, harmful variants.