Do both vaccines work?
Both vaccines went through large clinical trials. Pfizer enrolled close to 44,000 people and Moderna included 30,000. Half of the participants were given a placebo. Both manufacturers reported an efficacy of around 94.5 percent. in the Pfizer trial, 162 of 170 infections were in the placebo group. In Moderna's case, 90 of 95 were in the placebo group. The vaccines even appear to protect against severe disease in the few people who developed COVID-19.
Efficacy is just a fancy word for effectiveness, right?
Efficacy is used in a clinical trial sense. Effectiveness of a vaccine is determined from the point the general population is vaccinated. We won't know the effectiveness for many months.