How well do the first vaccines work?


The FDA reports that the vaccine made by Pfizer had an efficacy rate of 95 percent. That means that under the controlled conditions of the company’s phase 3 trial there were 95 percent fewer cases of COVID-19 in the group of people who got the vaccine compared to the group of people who got the placebo.

The FDA reports that the vaccine made by Moderna had a similar efficacy rate to Pfizer’s, and that the vaccine’s efficacy rates were similar across genders, age groups, racial and ethnic groups, and groups with comorbidities.

The FDA reports that the Johnson & Johnson vaccine had an efficacy rate at preventing moderate to severe COVID-19 of 66 percent worldwide, 72 percent in the United States, and 64 percent in South Africa where a new virus variant has become prevalent. This efficacy rate was similar for all major racial and ethnic groups and all age groups, but the efficacy dropped to 59 percent for groups with comorbidities.

According to the FDA, all three vaccines were nearly 100 percent efficacious at preventing hospitalization and death in the clinical trial populations. This may be the most significant finding of the clinical trials. It suggests that all of these vaccines can sharply reduce the severity of COVID-19 and ease the burden on hospitals.

(Updated 3/1/21)

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