Israel will start offering a fourth dose of the coronavirus vaccine to people aged 60 and over, becoming the first country in the world to widely disseminate the extra jab to fight off the omicron strain.

The fourth dose will also be made available to medical staff who had their last jab at least four months ago, Prime Minister Naftali Bennett said in a press conference on Sunday. Last week, Israel approved the extra shot for people who are immunocompromised, as well as residents of nursing homes and patients in geriatric wards.

New daily cases, which topped 5,000 last week in the country of 9.5 million, are expected to quadruple by the end of the week, Bennett said. The caseload could reach as many as 50,000 cases a day, he said, or nearly five times the previous peak. Critical cases remain well below previous records but have started to creep up over the past week.

“We must keep our eye on the ball, and act swiftly and decisively if we want to continue engaging and working with the country open as much as possible throughout this pandemic,” Bennett said.

Israel’s vaccination campaigns have been ahead of the curve, with the country the first to inoculate the majority of its population and the most aggressive in administering booster shots last year. But the notion of a fourth dose has run into turbulence because of the lack of solid data on omicron or the efficacy of a fourth dose.

Bennett last month announced a plan to immunize everyone 60 and over, but implementation was held up because of pushback by some expert advisers. At the same time, Israel says it has data suggesting immunity has waned in people in that age group who received boosters beginning in August. And some advisers say even without the data, Israel should take action because the variant is so contagious.