Jerusalem,  Israel has approved a fourth dose of the Covid vaccine for people aged 60 years old and above and medical staff, as the country continues to see an unprecedented surge in fresh cases.

Israel's Pandemic Response Committee had already issued a recommendation to proceed with the new booster shot on December 21, and was, last week, authorised for immunosuppressed patients and residents of retirement homes, the Jerusalem Post reported.

Those wanting to take the fourth booster must be over the age of 60 and should have received the third vaccine at least six months earlier.

"The decision (for elderly) was made based on the best professional considerations and after the Health Ministry consulted with experts," Prime Minister Naftali Bennett was quoted as saying on Sunday evening.

According to Bennett, Israel may face 50,000 new cases a day in the upcoming days, or about five times more than what the country experienced in previous waves.

The concern was earlier echoed by Weizmann Institute of Science Prof. Eran Segal who said that more than 40 per cent of Israel's population could be infected with the Omicron variant within the next three weeks.

"At the national level mass infection is inevitable," Segal wrote on Twitter. "Current restrictions are too weak in light of such a contagious virus."

However, vaccines continued to be very effective against serious symptoms, Segal said.

"On a personal level you can defend yourself," he said. "The vaccine and booster protect excellently from severe illness."

Israel recorded almost 27,000 new cases in the past week, marking a 200 per cent increase compared with the previous week, the report said.

The number of patients in serious condition rose, but in a more limited way.

As of Sunday night, there were 114 patients in serious condition. For most of the past two weeks the figure fluctuated between 80 and 90. On Saturday night, there were 101.

The current data in Israel seemed to confirm that Omicron is less violent than Delta, Segal said.

"Early yet encouraging data of fewer (approximately 10) daily critically ill patients compared to Delta wave (approximately 70) at similar case rates," he tweeted. "If these ratios hold, we should be below past hospitalisation peak."

While more than 40 per cent of the new virus carriers identified in the past week had received a booster, most patients in serious condition were not vaccinated at all (88) or were vaccinated more than six months earlier (six), with 21 of them inoculated also with a booster, all of them over 60.

Israel's Health Ministry has also signed a contract to buy the Molnupiravir antiviral treatment. The country has also started to administer the antiviral pill produced by Pfizer.