Pfizer's COVID-19 vaccine effectiveness drops after 6 months: study
CTV
The effectiveness of the Pfizer Inc /BioNTech SE vaccine in preventing infection by the coronavirus dropped to 47% from 88% six months after the second dose, according to data published on Monday that U.S. health agencies considered when deciding on the need for booster shots.
The data, which was published in the Lancet medical journal, had been previously released in August ahead of peer review.
The analysis showed that the vaccine's effectiveness in preventing hospitalization and death remained high at 90% for at least six months, even against the highly contagious Delta variant of the coronavirus.
The data suggests that the drop is due to waning efficacy, rather than more contagious variants, researchers said.
Researchers from Pfizer and Kaiser Permanente studied electronic health records of roughly 3.4 million people who were members of Kaiser Permanente Southern California between December 2020 - when the vaccine first became available - and August of 2021.
