(The Hill) – An Israeli study looking into the effects of a fourth total, or second booster, of the Pfizer-BioNTech COVID-19 vaccine showed with a “high degree of certainty” it’s safe and increased antibodies by fivefold one week post-vaccination, Israeli Prime Minister Naftali Bennett announced, per Reuters.

The Israeli government on Tuesday released the preliminary results of the trial, which .give insight to how an additional booster may help offset the impact of the hyper-contagious omicron variant, reports The Washington Post.

Bennett said the preliminary results showed “a very high likelihood that the fourth dose will protect vaccinated people to a great degree against infection to some degree and against severe symptoms,” according to the Post.

Bennett said at Sheba Medical Center, “A week into the fourth dose, we know to a higher degree of certainty that the fourth dose is safe,” adding, “The second piece of news: 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. This most likely means a significant increase against infection and… hospitalization and [severe] symptoms,” reports Reuters. 

Side effects reported from the vaccine were similar to those of the second and third shots. Recipients reported fever, fatigue, and headaches, notes Reuters. 

A separate group is set to receive Moderna’s vaccine—after initially having gotten three Pfizer-BioNTech shots—for their fourth dose this week and data from that group will soon follow up with the question of a potential superior immune response by mixing-and-matching vaccinations, a Sheba Medical Center spokesman states, according to the Post.

The Israeli government announced on Sunday that Israel will offer a fourth COVID-19 vaccine dose to health care workers and individuals 60 years old and older in an effort to bolster protection amid the omicron wave of the pandemic.

Eligible individuals can receive the fourth jab if they received their previous dose at least four months ago.

Bennett called on all eligible individuals to get the second booster before praising his country for being a leader in vaccination efforts.

“Israel will once again be pioneering the global vaccination effort. Omicron is not delta — it’s a different ballgame altogether. We must keep our eye on the ball, act swiftly and decisively if we want to continue engaging and working with an open country as much as possible throughout this pandemic,” Bennett said.