Pfizer Says COVID-19 Vaccine 90% Effective Against Virus

Pharmaceutical giant Pfizer has announced that its COVID-19 vaccine successfully prevented 90% of infections compared to a placebo, a more positive result than experts expected.

The analysis is based on 94 cases of infection with SARS-CoV-2, the virus that causes COVID-19, among both the vaccinated and placebo groups. Experts had set a minimum threshold of 60% effectiveness for vaccines to be considered for emergency authorization or approval. The company’s trial included data from 38,955 of the total 43,538 volunteers who enrolled.

Pfizer is the first company to release results from its COVID-19 vaccine, part of a planned interim analysis by an independent data safety monitoring board that is reviewing all of the handful of vaccine candidates from different companies that are currently being tested in people. The findings represent results collected seven days after the second of Pfizer’s two-shot regimen.

Pfizer, which developed and tested its vaccine with German company BioNTech, said in a release that it will continue following people in the study for a couple more weeks, until the middle of November, when everyone in the study will have been followed for at least two months. That’s the timeframe the Food and Drug Administration is requiring for COVID-19 vaccines before considering them for emergency authorization or approval.

The results represent a victory not only for public health but for science as well. The companies’ vaccine is based on a new technology that relies on a genetic material known as mRNA. No mRNA-based vaccines have received approval from the FDA yet, although several are being tested for other diseases. The results are a testament to the benefits of the platform — using mRNA speeds up development of a vaccine since the process does not require growing vast amounts of virus.

Instead, vaccine developers only needed the genetic sequence of SARS-CoV-2, which became available in January, to start building a vaccine. Other companies, including Massachusetts-based Moderna, and vaccine giant Sanofi, are also testing mRNA COVID-19 vaccines.

This is a developing story and will be updated throughout the day.