4th Vaccine Dose Has Reduced Efficacy Against Omicron: Israeli Study

Israel’s largest hospital, Sheba Medical Center at Tel Hashomer, released preliminary results Monday from a study showing that the fourth COVID-19 vaccine dose has low efficacy in warding off the omicron variant. The study, launched in late December, compared the immunization and serology data of 270 hospital staff members who received the fourth dose of the Pfizer or Moderna vaccine to that of more than 5,700 hospital workers who did not receive the fourth shot. “It turned out that the vaccine, which was very effective against the previous variants, is less effective against the omicron,” said the study’s leader, Prof. Gili Regev-Yochay, head of the infection prevention and control unit at Sheba. “The results indicate a significant increase in antibody levels, but this protection level is only partially effective against the omicron, which is relatively resistant to the vaccine,” she added. More than 537,000 people have been vaccinated in Israel with the fourth booster shot, most of them aged 60 and over. As of January 16, the biweekly number of confirmed new cases in Israel had grown more than 902% relative to the previous 14 days, and as of January 10, close to 88% of analyzed cases over the previous two weeks were of the omicron variant.