A fourth dose of a Covid-19 vaccine boosts antibodies but isn’t enough to prevent Omicron infections, according to a preliminary study in Israel.
Researchers at Sheba Medical Center near Tel Aviv studied the effect of the 
Pfizer (ticker: PFE) vaccine on 154 medical staff after two weeks, and the 
Moderna (MRNA) booster on 120 volunteers after one week, 
the Times of Israel reported.