Will Trials Alter the 90% Efficacy of Pfizer Vaccine?

Pfizer and BioNTech said they had identified 94 cases of COVID-19 among 43,538 trial participants.
The split of cases between the groups suggested that the vaccine was more than 90% effective at preventing disease.
The trial will continue until a total of 164 COVID-19 cases are detected, so initial estimates of the vaccine’s effectiveness could change.
Pfizer and BioNTech reported that 42% of participants had racially and ethnically diverse backgrounds.

Scientists have greeted with cautious...