Israel on Sunday began offering a Covid-19 booster to children as young as 12.
Its prime minister said the decision one month ago to offer boosters to older people had slowed a rise in severe illness caused by the Delta variant.
Israeli health officials said the effectiveness of the second dose of the Pfizer-BioNTech vaccine waned six months after administration, making a booster necessary.
“The third dose brings us to the level of protection achieved by the second dose, when it was fresh,” said Dr Sharon Alroy-Preis, head of public health at Israel’s Ministry of Health.
“That means, people are 10 times more protected after the third vaccine dose,” she said in a news conference held to announce the expanded booster drive.
People become eligible for the third dose five months after having their second one.
The interval is shorter than that in the US, where eight months must elapse between the second and third doses. A reduction is being considered.
Israel began administering the booster to its older population a month ago, to curb the spread of the highly contagious Delta variant.
The age of eligibility has been gradually lowered, and stood at 30 before the announcement on Sunday.
Two million people have received three doses. Israel’s population is about nine million.
“There are already results: the increase in severe morbidity has begun to slow,” Prime Minister Naftali Bennett said in a statement.
“But we have to complete third doses for all of our citizens. I call on those aged 12 and up to go out and immediately take the third shot.”
Israel, the UAE and other countries have pressed ahead with booster plans despite opposition from the World Health Organisation, which said more people should receive their first dose before others have their third.
The US has said it will offer booster doses to all Americans, citing data showing diminishing protection. Canada, France and Germany have also planned booster campaigns.