Israeli Prime Minister Naftali Bennett visits Sheba Tel HaShomer Hospital in Tel Aviv, Israel January 4, 2022. Ohad Zweigenberg/Pool via REUTERS

A fourth dose of the COVID-19 vaccine led to a fivefold rise in the number of antibodies a week after the jabs were administered, Prime Minister Naftali Bennett announced Tuesday, citing the preliminary results of an Israeli clinical trial.

“A week into the fourth dose, we know at a higher degree of certainty that the fourth dose is safe,” Bennett said at Israel’s Sheba Medical Center, which is heading a world-leading trial to determine the efficacy of a second booster. “A week after the administration of the fourth dose, we see a fivefold increase in the number of antibodies in the vaccinated person. This most likely means a significant increase in the protection against infection and against severe hospitalization and symptoms.”

Bennett remarked that previous research conducted by the Sheba Medical Center showed a high degree of correlation between the number of antibodies in the blood and the protection of infection and severe symptoms. Israel recorded over 10,000 new daily coronavirus cases on Monday, a surge of 3,444 cases from the previous day.

“Simply said, the fourth dose is secure. The fourth dose works,” Bennett added. “The Omicron wave is now really growing, and we are expecting tens of thousands of confirmed cases in the next few days. The good news is that the vaccines work, so those who are properly vaccinated and are wearing a mask probably will not get seriously ill, and this will pass within a few days. So, it’s in our hands.”

Bennett presented initial data from the trial, which was conducted among a group of 150 Sheba health workers to test the efficacy of a fourth vaccine shot in producing antibodies and safety. Participants had received the third vaccine dose before the end of August and had shown serological results under the 700 mark.

The initial trial results were presented publicly two days after Israel approved the administration of a fourth dose of the COVID-19 vaccine to all adults over 60, and medical workers, who received the previous dose at least four months ago.

Bennett said that since Israel started to offer the fourth shot to certain populations on Sunday, over 100,000 Israelis have registered to be vaccinated, or have already been jabbed. On Monday, about 20,000  eligible adults got a second booster.

“In the next few days we are going to share this [data] with the world,” Bennett said.