In a recent piece, I likened a society that’s reopening while partially vaccinated to a ship approaching an iceberg. The ship is the return to normal life and the viral exposure that it brings; the iceberg is the population of unvaccinated people. Precautions such as social distancing can slow the speed of the ship, and vaccination can shrink the size of the iceberg. But, in any reopening society that’s failed to vaccinate everyone, a collision between the virus and the vulnerable is inevitable. Because of its exceptional transmissibility, the Delta variant is almost certain to intensify the force of the collision. The U.K., by postponing a full reopening, is trying to soften the blow. But the U.S. is pressing ahead—perhaps out of hubris, or because officials hope that our vaccination campaign can outrun the spread of Delta. Last week, New York and California, among the pandemic’s hardest-hit states, did away with virtually all restrictions. Meanwhile, states with half the vaccination rates of New York or California have been open for weeks. A lot depends on where, and how fast, Delta is spreading... And yet, the pace of vaccinations hasn’t picked back up. Topol, for his part, believes that a major impediment to wider vaccination is the fact that the F.D.A. has not yet fully approved the covid vaccines; right now, they’ve received only an emergency-use authorization, or E.U.A. About a third of unvaccinated Americans say that F.D.A. approval would make them more likely to get immunized. Full approval could also pave a clearer path for vaccine mandates in schools, businesses, and the military. Topol argues that mandates would allow us to build a Delta wall more quickly—along with walls for Epsilon, Zeta, and the rest of the Greek alphabet. Both Pfizer and Moderna have applied for F.D.A. approval, but it’s unclear how soon they will receive it; the usual process takes six to ten months. “Hundreds of millions of people have safely taken these vaccines, but there’s still a perception among some that they’re experimental,” Topol said. “E.U.A. versus full approval may sound like semantics, but it’s actually a B.F.D.”