A fourth dose of COVID-19 vaccine given to people over 60 in Israel made them three times more resistant to serious illness than those who have had three vaccinations in the same age group, Israel's Health Ministry said on Sunday.
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.
The ministry said on Sunday the study it conducted with several major Israeli universities and the Sheba centre compared 400,000 people over 60 who received the second booster with 600,000 people in the age group who were given a third shot more than four months ago.
As elsewhere, Israel has seen COVID-19 cases spiral due to Omicron, but it has logged no deaths from the variant.
Meanwhile, the Omicron variant has moved the COVID-19 pandemic into a new phase and could bring it to an end in Europe, the WHO Europe director said on Sunday.
"It's plausible that the region is moving towards a kind of pandemic endgame," Hans Kluge told AFP in an interview, adding that Omicron could infect 60 per cent of Europeans by March.
Once the current surge of Omicron sweeping across Europe subsides, "there will be for quite some weeks and months a global immunity, either thanks to the vaccine or because people have immunity due to the infection, and also lowering seasonality".
"We anticipate that there will be a period of quiet before COVID-19 may come back towards the end of the year, but not necessarily the pandemic coming back," Mr Kluge said.
Top US scientist Anthony Fauci expressed similar optimism on Sunday, telling ABC News talk show This Week that with COVID-19 cases coming down "rather sharply" in parts of the United States, "things are looking good".