Covid Shots Come in Bulk. The World Needs Single Servings

The rapid development of Covid-19 vaccines is one of medicine’s greatest achievements, but distribution hasn’t been easy. Vials full of doses often must be kept in extreme cold, and once opened have to be used quickly, sometimes prompting health workers to run out into the street looking for someone to take the leftovers.

Now vaccination campaigns in the U.S. and some other countries are moving from mass demand to more targeted efforts to reach the hesitant -- and doctors want easier ways to deliver shots.