Sheba Hospital tried a fourth injection on more than 270 medical staff this month, with 154 receiving the Pfizer jab and 120 receiving Moderna.

The researchers disclosed on Monday that both groups had a “significantly larger” boost in antibodies than after the third injection — but not enough to prevent Omicron, the most recent type responsible for the vast majority of infections worldwide.

“Despite improved antibody levels, the fourth vaccine only provides a limited resistance against the virus,” said Dr. Gili Regev-Yochay, director of the hospital’s infectious disease section and the study’s main author.

“Many infected with Omicron received the fourth treatment,” she stated of the research. “Although slightly less than in the control group, there were still a number of infections.”

“The vaccinations, which were more successful against prior versions, give less protection vs Omicron,” Regev-Yochay said, adding that the immunizations are “not good enough” to prevent the new, less severe type.

The findings have not yet been published and do not contain any particular information.

However, the study highlighted concerns about Israel’s choice to be the first in the world — and only the fourth in the world — to administer a second booster injection to its over-60 population.

According to the government, nearly 500,000 people have gotten the second booster shot in recent weeks. Despite the fact that 80 percent of Israel’s adult inhabitants have had two doses and more than half have been boosted, the country has lately recorded record-high infections.

Sheba Hospital urged for “continuing the immunisation programme… even if the vaccine does not give maximum protection against being infected with the variation” hours after the results were released.

According to the Times of Israel, the hospital was compelled to issue the statement after the Health Ministry was dissatisfied with the study’s findings.

Dr. Nahman Ash, head of Israel’s Ministry of Health, also stressed that the findings did not imply that the fourth-shot attempt was a mistake.

“It restores the level of antibodies to where they were before the start of the third booster.” That is really important, especially among the elderly,” he told Channel 13 TV.

The Israeli government announced on Tuesday that the mandated quarantine period will be reduced from seven to five days in order to keep the economy operating.

“This decision will allow us to continue defending public health on the one hand, and to keep the economy moving at this time, even if it is tough, so that we can safely pass through this wave,” Prime Minister Naftali Bennett stated.