Outside, in large block letters, the wall of the trailer reads: "GET TESTED. GET TREATED. CRUSH COVID.” Inside, leathery recliners cradle patients as a freshly mixed concoction drips into their veins: a combination of two monoclonal antibodies once used so rarely that when U.S. President Donald Trump got it last October, it ignited accusations of special treatment.

Now, amid the delta variant surge, the cocktail is rapidly becoming a more common, even routine medical response to a positive coronavirus test in a high-risk patient. Federal and state officials are promoting it, particularly in hard-hit areas, and demand has exploded from a trickle to more than 120,000 doses a week by the latest count from its maker, Regeneron Pharmaceuticals Inc.

The company’s combination was bolstered by recent data showing that it cuts the risk of hospitalization or death by roughly 70% in high-risk patients, and can reduce the chance of infection among a patient’s household members by more than 80%. Further fueling its momentum: a recently added option to deliver it in quick shots as well as the slower, more logistically complex infusions.