2020

Pfizer–BioNTech COVID-19 vaccine

Pfizer and BioNTech announce greater than 90% interim efficacy for BNT162b2

The headline percentage rested on 94 symptomatic cases split between two blinded groups — and the companies still lacked the safety follow-up needed even to file with the FDA.

9 November 2020: the first interim readout

Pfizer and BioNTech announced on 9 November 2020 that the first interim analysis of their ongoing Phase III trial had found BNT162b2 more than 90% effective at preventing symptomatic COVID-19 in participants with no evidence of prior infection.

An independent data-monitoring committee had run that analysis the previous day. The estimate rested on 94 confirmed COVID-19 cases distributed across the vaccine and placebo groups, counted from seven days after the second dose.

What the companies said they still lacked

The trial was continuing, and the companies stressed that the efficacy estimate could change.

43,538 participants had enrolled and 38,955 had received a second dose by 8 November. Even so, the program had not yet reached the FDA's required median two-month safety follow-up for an emergency-use application.

Interim data, not an authorization

Nothing was authorized and nobody was vaccinated because of the release. It was a company press statement carrying interim numbers, not a regulatory decision or a peer-reviewed paper.

The finding concerned prevention of symptomatic COVID-19 under the trial's own endpoint. It did not establish sterilizing immunity or prevention of transmission.

The widely repeated 95% belongs to a later document, not this one: the final analysis reported 95.0% efficacy against symptomatic COVID-19 after dose two, with a 95% confidence interval of 90.3% to 97.6%.

Sources

Researched 23 Aug 2026 6 sources 2 audit passes Date corrected

How this was checked

Researched from the web into a fact sheet, rewritten from that sheet, then audited against it by a different model. How the pipeline works →

Date corrected. The research places this at 2020-11-09.

What the sources leave uncertain

“First successful Phase III trial” is imprecise. This was the first publicly announced positive interim efficacy result from a Phase III COVID-19 vaccine trial, not the completion of the trial or a peer-reviewed final result.
The November 9 figure was greater than 90%. The widely cited 95% estimate came from the later final analysis and publication.