Amid Covid-19 case surges in parts of the country with low vaccination rates and growing concerns over the highly transmissible Delta variant, the Centers for Disease Control and Prevention on Tuesday announced new guidance saying people in the\u0026nbsp;U.S. who are fully vaccinated should wear face masks in indoor public places in certain parts of the country and that indoor masks will be recommended in school settings in the fall.\r\n\r\nThe CDC cited emerging information about the Delta variant\u0026#039;s ability to spread among vaccinated people, with CDC Director Dr. Rochelle Walensky saying\u0026nbsp;that unlike earlier variants of the virus, a vaccinated person infected with the Delta variant has levels of the virus that are \u0022indistinguishable\u0022 from those in unvaccinated people who are infected.\u0026nbsp;\r\n\r\n“This new science is worrisome and unfortunately warrants an update to our recommendation. It is concerning enough that we feel like we have to act.\u0022\u0026nbsp;\r\n—Dr. Rochelle Walensky, CDC\r\n\r\n“This new science is worrisome and unfortunately warrants an update to our recommendation,\u0022\u0026nbsp;Walensky said of the new, unpublished\u0026nbsp;data, which the CDC gathered in recent days from 100 samples.\u0026nbsp;\u0022It is concerning enough that we feel like we have to act.\u0022\r\n\r\nIn addition to advising teachers, school staff, students, and visitors to schools to wear masks inside regardless of vaccination status, the CDC recommended that vaccinated people wear masks in indoor public spaces if they have\u0026nbsp;young children who can\u0026#039;t\u0026nbsp;be vaccinated or household members who are immunocompromised or otherwise vulnerable.\r\n\r\nThe new guidelines come two months after the CDC said that vaccinated people could go without masks in both indoor and outdoor settings, launching an effort by the Biden administration to incentivize vaccinations by suggesting they were the key to \u0022getting everything back to normal.\u0022\r\n\r\n\u0022The rule is very simple: Get vaccinated or wear a mask until you do. It’s vax’ed or masked,\u0022 President Joe\u0026nbsp;Biden said in May during a celebratory event at the White House, the tone and message of which drew alarm from some public health experts.\r\n\r\nNational Nurses United—the country\u0026#039;s largest nurses\u0026nbsp;union—was among those that denounced the CDC\u0026#039;s claim that vaccinated people could safely go unmasked in all public places, saying the pandemic was \u0022far from over\u0022 and noting that the same week the earlier guidance was released, the CDC had reported a 16% increase in daily new cases over the previous week.\r\n\r\nOn Tuesday, the Washington Post reported that confirmed coronavirus infections have quadrupled nationwide since the beginning of July. Officials recorded about 13,000 cases per day at the start of the month and are now recording about 54,000 per day. Less than half of the U.S. population has been fully vaccinated.\r\n\r\nThe CDC\u0026#039;s new guidance came a day after officials in New York City and California announced that public employees will be required to be vaccinated or undergo weekly testing; California\u0026#039;s mandate applies to public- and private-sector healthcare workers as well.\r\n\r\nThe White House also said Monday that it will continue restricting the entry of travelers from Europe, while the CDC urged Americans to avoid traveling to Spain and Portugal, which have seen Covid-19 cases rise by 74% and 18%, respectively, in the last two weeks.\r\n\r\nThe CDC\u0026#039;s new guidance was applauded Tuesday by public health experts, some of whom had expressed concern about the loosening of guidelines in May.\r\n\r\n\u0022About damn time,\u0022 Eric Feigl-Ding, an epidemiologist at the Federation of American Scientists, tweeted, adding:\u0026nbsp;\u0022Glad [the CDC] reversed course. But I worry it might be harder for compliance now than if we kept masks in place in May.\u0022\r\n\r\nJeremy Faust, an emergency physician in Boston, rejected some news outlets\u0026#039; reporting that the CDC had \u0022backtracked\u0022 on its earlier guidance, in which unvaccinated people were advised to continue masking in public settings.\r\n\r\n\r\n\r\nThe call for people to continue masking regardless of vaccination status \u0022is key,\u0022 said CNN medical analyst Leana Wen, \u0022as [the] honor system does not work.\u0022\r\n\r\nLuis Schang, a virologist at Cornell University, emphasized that despite the new data about the Delta variant\u0026#039;s viral load, vaccines are still shown to be effective at preventing the worst outcomes of the disease and that vaccination rates are rising.\u0026nbsp;\r\n\r\n\u0022It\u0026#039;s not a permanent thing. That\u0026#039;s an important thing to highlight,\u0022\u0026nbsp;Schang told the Post.\u0026nbsp;\u0022This is not something we have to do for years. This is weeks, perhaps a couple of months.\u0022\r\n\r\nWalensky also said the mask guidance is meant to be a \u0022temporary\u0026nbsp;measure.\u0022\r\n\r\n\u0022What we really need to do to drive down these transmissions in the areas of high transmission is to get more and more people vaccinated and in the meantime, to use masks,\u0022 the CDC director said.