The global battle against Covid-19 may be on the verge of getting a game-changing new weapon: virus-fighting pills. But questions remain on how well these up-and-coming treatments will work in the real world, and what their impact on the pandemic will be. Hundreds of Covid-19 treatments are currently in development, but in recent weeks major pharmaceutical firms have announced promising results for two oral pills, paving the way for their potential widespread use. Early this month, a drug from US company Merck became the world’s first oral pill approved for Covid-19 after Britain recommended it for use in people with...