The scale of the administration’s approach puts the U.S. at odds with Israel and many European allies. Many foreign governments are requiring proof of vaccination for airline travel and restaurant dining, as well as stricter rules for travelers from southern Africa, where the omicron variant was first detected.

The Biden administration finds itself caught between measures supported by public health experts and the reality of what it can achieve politically in the face of widespread Republican opposition to vaccination requirements and mask mandates…

“We must do something because of politics, but we can’t do what would really work because of politics,” said Dr. Celine Gounder, an infectious disease specialist at New York University who advised the Biden transition team…

“Most of the measures discussed are extensions of existing policies, which will likely do very little to truly curb the effects of surging variants and those that threaten to escape current immunity,” said Dr. Kavita Patel, a physician who worked in the Obama administration.