Pfizer COVID-19 vaccine efficacy drops to 84% after 6 months, preprint study suggests

A new study involving the Pfizer-BioNTech COVID-19 vaccine suggests the jab’s efficacy drops to around 84% about six months after the second dose.

The data noted that vaccine efficacy peaked between 7 days and two months post-second dose at 96.2%. From two months to four months, efficacy fell to 90.1%, and from four months to six months, it further fell to 83.7%. Researchers calculated a decline in vaccine efficacy about an average of about 6% every two months. The study found that the vaccine overall achieved about 91% efficacy from seven days through six months post-second dose in study participants ages 12 and older.  "Ongoing follow-up is needed to understand the persistence of the vaccine effect over time, the need for booster dosing, and timing of such a dose," the study authors wrote, later adding that booster trials are currently underway.