'Lot of Infections' From Omicron After 4th Dose: Trial

Preliminary results are in on a clinical trial testing the efficacy of a fourth COVID shot, the world's first, and when it comes to omicron, that booster isn't doing the job researchers had hoped for. The Times of Israel reports that, in a study that began last month at Sheba Medical Center near Tel Aviv, a fourth dose does appear to boost antibody levels "slightly higher" than after a third one, but the vaccine doesn't seem to fend off breakthrough infections from omicron to the same degree it did with other variants. "We see many infected," says Dr. Gili Regev-Yochay, one of the scientists leading the study. "Granted, a bit less than in the control group, but still a lot of infections."

The bottom line when it comes to preventing breakthroughs, per Regev-Yochay: "The vaccine is excellent against ... alpha and delta, [but] for omicron it's not good enough." Per USA Today, the admittedly small trial involved 274 medical workers at the hospital who received their second booster shot in December—154 with the Pfizer-BioNTech variety, the rest with Moderna—after initially receiving three Pfizer shots. CNN notes there was also a control group not given any boosters. Regev-Yochay says she decided to release the preliminary results due to high public interest in the matter. Despite this development, she says she still thinks it's worthwhile to administer this second booster to "vulnerable populations."

Dr. Nahman Ash, who heads up Israel's Health Ministry, concurs, telling Channel 13 that the antibody boost is of "great importance, especially among the older population," per the AP. He notes, however, that health officials will consider the research as they decide whether to administer a fourth dose to the general population. Israel was the first country to approve a fourth dose for its most vulnerable citizens last month. The World Health Organization, meanwhile, has been urging countries to hold off on booster programs until all nations have access to initial doses of the vaccine. (More omicron variant stories.)