Pfizer and Moderna COVID-19 Vaccines Are 90% Effective in Real-World Setting

• A new study shows that the Pfizer-BioNTech and Moderna-NIAID vaccines are effective at preventing infections in the real world.
• The study was published March 29 in Morbidity and Mortality Weekly Report, a publication of the Centers for Disease Control and Prevention.
• Researchers found that a two-dose vaccine regimen was 90 percent effective at preventing infections 2 weeks after receiving the second dose.

A new study suggests that the COVID-19 vaccines developed by Pfizer-BioNTech and Moderna-NIAID are highly effective at preventing symptomatic and asymptomatic infections in real-world settings.

The study was published March 29 in Morbidity and Mortality Weekly Report, a publication of the Centers for Disease Control and Prevention (CDC).

Researchers found that a two-dose vaccine regimen was 90 percent effective at preventing infections 2 weeks after people received the second dose.

One dose was 80 percent effective 2 weeks after vaccination. This was based on a limited window between the first and second dose, so the study can’t show how effective one dose of the vaccine is long term.

These results are similar to those from earlier phase 3 clinical trials, which found an efficacy of more than 90 percent for both the Pfizer-BioNTech and Moderna-NIAID vaccines.

Efficacy is a measure of how well a vaccine works in the carefully controlled setting of a clinical trial.

Real-world effectiveness is sometimes lower due to a number of factors.

Dr. James H. Conway, a pediatric infectious disease specialist at the University of Wisconsin-Madison, said what we really care about is a vaccine’s effectiveness — its real-world potential.

With studies like this, “we’re starting to get a better sense of how powerful these vaccines are when people get out into the real world,” Conway said.

“So it should be extraordinarily reassuring to everybody that these vaccines work as well as we hoped they would,” he said.