First came the good news. The European Union authorised a third vaccine.
Then, the bad news. Regulators in country after country suggested restricting it to younger people until more testing was done.
The decisions marked the start of a delicate new phase of vaccination drives, one in which a growing menu of coronavirus vaccines was accompanied by contentious debates about who should be given which shots.
Those debates are a testament to the world’s good fortune in having several strong vaccines only a year into the pandemic. But every vaccine comes with its own idiosyncrasies, including gaps in clinical trial data. And that has thrown up agonizing choices for countries already struggling to administer shots, forcing health officials to weigh their qualms about certain vaccines with the need to inoculate people before dangerous variants take hold.
After the European Union authorized the AstraZeneca-Oxford vaccine last week, adding a third shot to the bloc’s arsenal, Germany, Italy,…