Israel begins trial of fourth coronavirus vaccine dose ahead of planned national campaign

The trial at Sheba Medical Center in central Israel involves 150 medical workers who received third doses before Aug. 20 and have antibody counts below 700, signifying low protection, according to a statement from the hospital. The trial is being carried out in conjunction with Israel's Health Ministry.

"It's one jab in the shoulder, but one giant leap for mankind," said Jacob Levee, director of the hospital's heart transplant unit and the first recipient of the fourth vaccine at Sheba.

He said he wanted to get vaccinated to protect his heart transplant patients, whose "immunity following the third dose has diminished significantly, so they're exposed," according to research at Sheba.

On Tuesday, Prime Minister Naftali Bennett announced that Israel would be the first country in the world to offer fourth Pfizer-BioNTech vaccine doses to citizens over the age of 60, people with compromised immune systems and health-care workers. He called on health-care facilities across the country to prepare to roll out the campaign, but the decision has not yet been approved by Health Ministry Director Nachman Ash.

The Sheba study will produce initial results within the coming days and weeks, which may help steer the next steps in the fourth-dose immunization campaign, said its head researcher, Gili Regev-Yochai.

"This research is very important because then we will have initial data about the safety," Regev-Yochai said.

One major unknown about coronavirus vaccines is whether, and with what frequency, additional doses will continue to generate strong immune system responses, as opposed to weaker or even immune-dampening effects, if administered too close to the previous shot.

Sheba Hospital spokesperson Steve Walz said the study is designed "to find out if indeed this fourth vaccine will show it produces enough antibodies to fend off omicron and delta," as well as whether there is any "adverse reaction," other than the usual post-vaccine side effects.

"The idea is before the government decides whether to go ahead with another vaccination campaign, to check the efficacy of this vaccine," he said.

The advisory board to Israel's coronavirus cabinet concluded last week that the potential benefits of a fourth vaccine dose far outweigh its risks. The board pointed to early signs that immunity has waned since the first Israelis received their third shot in the summer. It warned that, with the omicron variant spreading rapidly across the country and the globe, it could not afford to wait.

"We can't close our eyes and think happy thoughts," Health Minister Nitzan Horowitz said in an interview with public broadcaster Kan on Monday. He cited a rise in infections and serious illnesses caused by the omicron variant, mostly among the unvaccinated. "We have to prepare," he said.

According to Israeli Health Ministry data, 1,760 people tested positive on Sunday for the coronavirus, accounting for almost 2 percent of all tests performed. There are 87 people hospitalized in serious condition, including 38 on ventilators.

Early data from South Africa, where omicron first surged and has in recent days been receding, suggests that the variant may cause 80 percent fewer hospitalizations and instances of severe symptoms than delta and other previous variants.

But the head of the Africa Centers for Disease Control and Prevention warned that this might not be the case in all other countries.

"Let's be careful not to extrapolate what we [are] seeing in South Africa across the continent or across the world," Africa CDC Director John Nkengasong said Thursday.

On Friday, the United Kingdom reported 122,186 cases, a record high. One in 20 - a ratio that has perhaps grown to as many as 1 in 10 people - are believed to be carrying the virus in London, according to the Office for National Statistics.

Israeli health experts have said that even if omicron cases are milder than those in previous waves, the sheer number of infected people could overwhelm hospitals.

"In the past 10 days, the number of people who have tested positive for the omicron variant rose from 20 a day to 450. That is more than a twentyfold rise within 10 days," Eran Segal, a professor at the Weizmann Institute of Science and consultant to the Israeli coronavirus cabinet, said in an interview Sunday with the Israeli news site Ynet. "I anticipate that within a week we'll see thousands of people testing positive for omicron, and within two weeks we may cross the record high since the beginning of the pandemic - around 10,000 people testing positive daily."