NEW YORK (Reuters Breakingviews) - TROLLEY PROBLEM. Two U.S. health agencies recommended a pause in the use of Johnson & Johnson’s coronavirus vaccine because of a possible role in triggering extremely rare blood clots. Even so, the $10 billion fall in J&J’s market value is an overreaction. The $416 billion baby-powder maker isn’t aiming to make a profit from the vaccine during the pandemic anyway. With similar tiny but serious risks potentially attached to AstraZeneca’s nonprofit jab, it’s more an opportunity for Pfizer and Moderna. America has already agreed to purchase 600 million doses from the two companies, so they probably won’t sell many more stateside. And their vaccines are too costly for developing economies. Yet rich and middle-income countries still seeking contracts now have an additional reason to pick Pfizer and Moderna. That could be significant gravy for the profit-seeking firms. Pfizer alone estimated in January there would be $15 billion worth of vaccine revenue in 2021. There’s a bigger picture, too. Side effects from vaccines using messenger RNA, like the Pfizer and Moderna jabs, could still emerge. As of now, though, deploying mRNA technology to prevent other diseases is looking more appealing by the day. (By Robert Cyran)