This is a nice thread on the subject: twitter.com/nataliexdean/status/1310613…?...

What we still don't know for both Pfizer/BioNTech and Moderna vaccines: "A vaccine that prevents infection entirely provides indirect protection to others. If I can't get infected, I can't infect you. But it is possible to have a vaccine that prevents disease but individuals can still be infectious." (1) In that case, those at risk are only protected when they receive a vaccine, but still aren't when just those who they are in contact with received it. "Most Phase 3 trials are measuring efficacy to prevent disease as the primary analysis" (2) Not infection. The whole thread with more details, already written in September, before both announcements: twitter.com/nataliexdean/status/1310613… by: "Natalie E. Dean, PhD, Assistant Professor of Biostatistics at @UF specializing in emerging infectious diseases and vaccine study design. @HarvardBiostats PhD." (3) 1) twitter.com/nataliexdean/status/1310613… 2) twitter.com/nataliexdean/status/1310613… 3) twitter.com/nataliexdean