The front-runners in the vaccine race seem to be working far better than anyone expected. Pfizer and BioNTech announced this week that their vaccine had an efficacy rate of 95%. Moderna put the figure for its vaccine at 94.5%. In Russia, the makers of the Sputnik vaccine claimed their efficacy rate was over 90%.

¡°These are game changers,¡± said Dr. Gregory Poland, a vaccine researcher at the Mayo Clinic. ¡°We were all expecting 50 to 70%.¡± Indeed, the Food and Drug Administration had said it would consider granting emergency approval for vaccines that showed just 50% efficacy.

From the headlines, you might well assume that these vaccines - which some people may receive in a matter of weeks ¡ªwill protect 95 out of 100 people who get them. But that¡¯s not actually what the trials have shown. Exactly how the vaccines perform out in the real world will depend on a lot of factors we just don¡¯t have answers to yet ¡ª such as whether vaccinated people can get asymptomatic infections and how many people will get vaccinated.