(Israel21c via JNS) Israel’s Sheba Medical Center this week began the world’s first trial of a fourth dose of the Pfizer-BioNTech COVID-19 vaccine.

Sheba, the largest medical center in Israel and the Middle East, recruited 150 employees for the study. Each had received a third “booster” dose in August but now has a low antibody count of below 700, according to a hospital spokesman.

Led by Dr. Gili Regev-Yochay, director of Sheba’s Infectious Disease Epidemiology Unit, the study was approved by the Health Ministry’s Helsinki Committee, which oversees human medical trials.

Although the U.S. Food and Drug Administration has not yet approved a fourth Pfizer shot, Israel’s Pandemic Expert Committee wants to administer fourth shots to medical personnel and citizens over age 60, because the protection offered by the third dose seems to wear off at six months.

Regev-Yochay said her goal is to determine whether the fourth dose is effective in stimulating the production of antibodies and whether it is safe.

“This study is expected to shed light on the additional benefit of giving a fourth dose. We will [seek to] understand whether, and to whom, it is worth giving a fourth dose,” she said. “We will have safety data within a few days.”

The results will help guide Israel’s policy and that of the rest of the world as the omicron variant is causing a new wave of infections. Many experts believe the current formulation of the vaccine is ineffective against omicron.