Katherine Wu: “For the past year and a half, since the Covid-19 vaccines first became available—even as last summer’s reprieve gave way to Delta’s surge, then Omicron’s; even as the coronavirus continued to rack up mutations that lifted its speed and its stealth; even as millions of vaccinated Americans caught the pathogen and passed it on—there’s been one huge slice of solace to cling to: The shots we have are still doing an excellent job of staving off severe disease and death.”

