INTERNATIONAL: A fourth dose of COVID-19 vaccine boosts antibodies five-fold a week after the shot is administered, Israeli Prime Minister Naftali Bennett said on Tuesday (January 4), citing preliminary findings of an Israeli study.

"A week into the fourth dose we know to a higher degree of certainty that the fourth dose is safe," Bennett has said at Sheba Medical Center, which is giving second booster shots in a trial among its staff amid a nationwide surge in Omicron variant infections.

"The second piece of good news is that we know that a week after administration of a fourth dose, we see a five-fold increase in the number of antibodies in the vaccinated person," he told reporters.

"This most likely means a significant increase against infection and ...hospitalisation and severe symptoms," the prime minister has added.

Israel has played a leading role in studying the effects of COVID-19 vaccines, as the fastest country to roll out two-dose inoculations to a wide population a year ago and one of the first to give third shots as boosters. It is now administering fourth doses of the Pfizer/BioNTech vaccine to people over 60, health workers and immunocompromised patients.