An Israeli study will test the effectiveness of the fourth dose of the vaccine

A senior health ministry official said last week that the ministry would collect more data from other countries, particularly on the risk of serious illness from Omicron in the elderly, before deciding whether to give a fourth dose and to whom.

A second ministry official said on Monday that a decision could be made within days. Both officials requested anonymity to comment on the operation.

Also on Monday, the Israeli Ministry of Health formally approved another recommendation from the advisory board, shortening the period between giving a third booster dose after the second vaccine to three months out of five.

“Now, in light of the Omicron wave, there is a growing need to increase immunity levels among the general population as quickly as possible,” the ministry said in a statement, noting that other countries in Europe had done the same.

Most of Israel’s population has received at least two doses, but about a million eligible citizens have not yet received a third booster dose, out of a total population of nine million.