A fourth dose of the Covid-19 vaccine given to over-60s in Israel made them three times more resistant to serious illness than people with just one booster 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 on January 17 found the fourth jab increases antibodies to 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 on January 3 as Omicron swept the country, making it the first country to offer fourth doses on a widespread level.
The ministry said the study, 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.
Israel has seen Covid-19 cases spiral due to Omicron.
Germany has indicated it plans to administer a fourth dose to a wider section of its general population in the coming months to tackle Omicron.
The UK’s Joint Committee on Vaccination and Immunisation (JCVI) has said it is waiting for more data on waning immunity and effectiveness of the vaccination in reducing hospital admissions before it decides on offering a fourth jab.
Professor Adam Finn, professor of paediatrics at the University of Bristol and a member of the JCVI, has said that elderly adults “may need a further jab”.
Data released on Friday by the US Centre for Disease Control found that a third dose of the Pfizer and Moderna vaccines is more than 90 per cent effective against both the Delta and Omicron variants.
In the UK, a fourth dose is currently only available to people who have a severely weakened immune system.
