The White House has defended the decision to change course and reinstate certain masking guidelines amid the surging Delta variant of the coronavirus.

       The new directives suggest everyone in schools as well as vaccinated people in areas with lots of infections wear a mask, and are “based on evolving data” about the Delta variant, press secretary Jen Psaki told reported on Tuesday. Previously, the CDC had advised that vaccinated individuals could go maskless in most settings.

       “Our goal is to save their lives,” Ms Psaki told CBS News’s Weijia Jiang, who asked about whether the reversal might leave Americans with lingering doubts and a sense of “whiplash”.

       “Our response and the response of public health officials is to continue to provide updated guidance,” she said.

       “That’s exactly what they should be doing.”

       She also expressed frustration at the at least eight states which have explicitly prohibited mask mandates in schools.

       “I’m happy not to live in a state where that is the guidance,” she said. “This is new guidance that is being issued by the CDC today. I don’t know how it will influence local elected officials in these states, but I certainly hope for the health and wellbeing of the next generation, that they take a close look at the guidance.”

       On Tuesday, CDC director Dr Rochelle Walensky acknowledged that many may feel “tired” and “frustrated” with the evolving coronavirus guidelines, but they were necessary due to the evolving threat of the virus.

       New science shows that fully vaccinated people can still spread the virus, though the vast majority of those who spread and are sick with the virus are unvaccinated.

       Getting those who are unvaccinated, for reasons of poor access or personal reservation, to take the jab is even more important, now that the highly contagious Delta variant makes up eight in 10 samples of Covid found around the country, according to Dr Walensky.

       Average daily causes have been increasing since the summer, and are approaching the 65,000 or so daily rate not seen since last summer’s surge.

       As of Monday, the US had administered 342 million doses of the Covid vaccine, covering more than half the population and putting it in league with other rich nations who have a lion’s share of available doses.

       Still, daily vaccination rates have been falling since April, as many Americans refuse to take the treatment.