The mRNA vaccines are looking better and better

The protein-based vaccines have moved too slowly to matter so far. J&J’s and AstraZeneca’s vaccines are effective at preventing COVID-19—but a small number of recipients have developed a rare type of blood clot that appears to be linked to the adenovirus technology and may ultimately limit those shots’ use. Meanwhile, with more than 180 million doses administered in the U.S, the mRNA vaccines have proved astonishingly effective and extremely safe. The unusual blood clots have not appeared with Pfizer’s or Moderna’s mRNA technology. A year later, the risky bet definitely looks like a good one. The U.S. has ordered enough mRNA vaccines to inoculate its entire population. In that context, the CDC and FDA’s call to pause the J&J rollout this week is a blow to the American inoculation campaign, but hardly a devastating one. (J&J’s vaccine accounts for less than 5 percent of doses administered so far, and AstraZeneca’s has not yet been authorized in the U.S.) But the rest of the world has been banking on the J&J and AstraZeneca vaccines, which are both cheaper and easier to distribute because they don’t require the same cold storage as mRNA vaccines. If the blood-clot risk is real, the divide between the mRNA-vaccine haves and have-nots will only grow. The U.S. will be fine; the rest of the world will face difficult questions about balancing the risks and benefits of an affordable, good-but-not-best vaccine against a disease that has killed nearly 3 million people...