JERUSALEM—Prime Minister Naftali Bennett said on Sunday that Israel would offer a fourth dose of COVID-19 vaccine to people over 60 and to medical staff. Israel last week approved a fourth dose of the vaccine developed by Pfizer and BioNTech, a second booster, for people who are immune-compromised and the elderly living in care homes. “We now have a new layer of defense,” Bennett said in a televised news conference, adding that Israel’s top government medical official, whose approval is needed to expand the booster campaign, had signed off on the latest move. Earlier, the Health Ministry’s Director-General Nachman Ash said Israel could reach herd immunity as Omicron infections mounted and Merck & Co.’s molnupiravir anti-viral pill was approved for use in COVID-19 patients over 18. Herd immunity is the point at which a population is protected from a virus, either through vaccination or by people having developed antibodies by …