Tobias Schwarz/AFP via Getty Images This story is part of a group of stories called Finding the best ways to do good. In the past couple of weeks, experts and pundits have debated a big question surrounding the rollout of the Covid-19 vaccines from Pfizer/BioNTech and Moderna: Do we stick to two doses for every person, spaced a couple of weeks apart, as originally planned? Or should we go ahead and give out single doses to more people even when we’re not sure we’ll manage the second dose as planned — to get a shot in as many arms as possible, even if there’s less certainty about the efficacy of that approach?