According to a new Sheba Medical Center study, published in the peer-reviewed Lancet medical journal, COVID-19 infections were reduced by 75% among recipients of the Pfizer-BioNTech vaccine 15-28 days after getting the first dose. Moreover, the study indicated that the reduction in symptomatic infections was even higher, and stood at 85%. The study centered around 9,000 of Sheba’s caregivers, among whom about 7,000 received the first dose of the Pfizer-BioNTech COVID-19 vaccine in January. Only 170 recipients became infected during the two-week period. Of those who contracted the virus, 99 exhibited symptoms. 89 of those infected were not vaccinated.
“In real life, the data looks at least as good as in the clinical trials, and the first dose is even more effective than we thought,” said Prof. Gili Regev-Yochay, Director of the Infectious Diseases Unit at Sheba Medical Center and one of the authors of the study. According to Prof. Eyal Leshem, Director of Sheba’s Center for Travel & Tropical Medicine: “This is the first study assessing the efficacy of a single vaccine dose in real-life conditions, and it demonstrates early effectiveness even before the second dose is administered.”
Sheba Medical Center is now completing research on the impact of the second dose, which researchers still believe is essential, but according to the study, early reductions of COVID-19 rates provide support for delaying the second dose in countries facing vaccine shortages and scarce resources, so as to allow higher population coverage with a single dose. However, a longer follow-up is required to assess the long-lasting efficacy of a single dose in order to inform a second dose delay policy.