First Dose of Pfizer-BioNTech COVID-19 Vaccine Reduces Symptomatic Disease Significantly

February 19, 2021
John Parkinson

An Israeli study finds it had an 85% effect in lowering disease 2 to 4 weeks after administration of the initial vaccination.

The first dose of the Pfizer-BioNTech COVID-19 vaccine is showing it reduces symptomatic disease by 85%, 2 to 4 weeks after vaccination.

The findings were published in The Lancet.

“Our data show substantial early reductions in SARS-CoV-2 infection and symptomatic COVID-19 rates following first vaccine dose administration,” the investigators wrote.

The study was conducted in Israel at the Sheba Medical Center, which is the country’s largest hospital. The medical center has 9647 health care workers (HCWs), and the entire staff was eligible for vaccination, excluding those who had COVID-19 previously.

They began mass vaccination on December 19, 2020.

“Compared with a symptomatic COVID-19 rate of 5·0 per 10 000 person-days in unvaccinated HCWs, disease rates were 2·8 and 1·2 per 10 000 person-days on days 1–14 and days 15–28 after the first dose of the vaccine, respectively,” the investigators wrote about the results. “Adjusted rate reductions of COVID-19 disease were 47% (95% CI 17–66) and 85% (71–92) for days 1–14 and days 15–28 after the first dose, respectively.”

The data suggested that during this period of limited vaccine supply, the investigators said it lent support for getting the first vaccine to more people, even if there are delays in getting the second dose.

“Early reductions of COVID-19 rates provide support of delaying the second dose in countries facing vaccine shortages and scarce resources, so as to allow higher population coverage with a single dose,” the investigators concluded.