The effectiveness of the Pfizer-BioNTech COVID-19 vaccine waned over six months, but experts say the data still don't point to an immediate need for booster shots.
The study, which hasn't yet been peer-reviewed or published in a medical journal, found that the vaccine was 97 percent effective at preventing severe disease from COVID-19 for at least six months — but the effectiveness against any symptomatic illness dropped from 96 percent to 84 percent in the same period, falling by about 6 percent every two months.
"I was generally encouraged by the results of the paper," said the lead study author, Dr. Stephen Thomas, a coordinating investigator for the Pfizer vaccine trial and director of the SUNY Upstate Institute for Global Health & Translational Science in New York.
More Coronavirus Vaccine Coverae
He said the expectation was always that the vaccine's protection was going to wane. The big question, he said, was whether it would wane to a degree that would affect the so-called public health burden of the disease, specifically hospitalizations and deaths. So far, that doesn't appear to be the case.