A nurse prepares a fourth dose of coronavirus disease (COVID-19) vaccine as part of a trial in Israel, at Sheba Medical Center in Ramat Gan, Israel December 27, 2021. (Photo: Reuters)

The ministry also said the fourth dose, or second booster, made people over 60 twice as resistant to infection than those in the age group who received three shots of the vaccine.

A preliminary study published by Israel's Sheba medical centre last Monday found that the fourth shot increases antibodies to even higher levels than the third but "probably" not to the point that it could completely fend off the highly transmissible Omicron variant.

Israel began offering a fourth dose of the Pfizer/BioNtech vaccine to people over 60 earlier this month as Omicron swept the country.