The second Pfizer/BioNTech vaccine is better than the first

Pfizer and BioNTech’s search for a Covid-19 vaccine is clearly evolving: On July 27, for instance, the companies announced they would conduct a 30,000-patient trial for a vaccine. But, surprisingly, the vaccine they'll be using for this trial is different than the one the companies presented data for on July 1, STAT’s Matthew Herper writes. That’s because the second vaccine seems to trigger substantially fewer adverse events.

“Obviously, the better tolerated the vaccine, the more I think it will encourage the public acceptance of a broad immunization,” a top Pfizer vaccine development exec told STAT. “Both would have been great candidates. We were fortunate that [the second vaccine] actually satisfied having both a favorable immune profile and fewer reactions.”