Pfizer and BioNTech’s favored Covid-19 vaccine has fewer side effects than their first

Pfizer and BioNTech’s favored Covid-19 vaccine has fewer side effects than their first

Source: 
Stat
snippet: 

Pfizer and BioNTech surprised many industry watchers on July 27 when they announced they would conduct a large-scale study of a vaccine for Covid-19. The surprise? The vaccine that would be tested in a 30,000-patient trial wasn’t the one for which the companies had presented data on July 1.