In front of baskets of tomatoes and peppers, near a sizzling burrito grill, the “promotoras” stop masked shoppers at a busy Latino farmers market: Want to test a COVID-19 vaccine?Aided by Spanish-speaking “health promoters” and Black pastors, a stepped-up effort is underway around the U.S. to recruit minorities to ensure potential vaccines against the scourge are tested in the populations most ravaged by the virus.Many