Israeli study shows 4th shot of COVID-19 vaccine not able to block Omicron

A fourth shot of COVID-19 vaccine boosts antibodies to even higher levels than the third jab but it likely is not enough to prevent Omicron infections, according to a preliminary study in Israel.

The vaccines led to a increase in the number of antibodies "even a little bit higher than what we had after the third dose", said Regev-Yochay, adding that the results were preliminary and not yet published.

Israel was the fastest country to roll out initial vaccinations a year ago and last month started offering a fourth shot, or a second booster, to the most vulnerable, high-risk groups.