Israeli Hospital to Begin Clinical Trial on Fourth Shot of COVID Vaccine

150 hospital employees will take part in a trial examining effects of another booster shot, as restrictions return amid spread of omicron variant

Ido Efrati
Ido Efrati
A nurse draws a dose of a COVID vaccine into a syringe on Sunday.
A nurse draws a dose of a COVID vaccine into a syringe on Sunday.Credit: Tomer Appelbaum
Ido Efrati
Ido Efrati

An Israeli hospital is set to launch a clinical trial to test the effectiveness of a fourth coronavirus vaccine shot in the coming days, as restrictions are being reimposed due to the highly contagious omicron variant.

The trial at Sheba Medical Center, Tel Hashomer, will be led by Prof. Gili Regev-Yochay, director of the hospital’s Infectious Disease Epidemiology Unit, and will involve several phases. The research subjects will be 150 members of the hospital’s medical staff from whom serological testing data was collected over the past year, since vaccinations began in Israel.

To qualify for the trial, participants must have received their third shot by August 20, and serological testing must show that they have a certain level of antibodies. The trial will not, at this point, include people who have recovered from COVID-19. It is a preliminary trial in a broader research project expected to include further studies.

On Saturday, Health Minister Nitzan Horowitz said the advisory panel on the coronavirus would be meeting this week to discuss whether it was necessary to begin giving fourth shots to older Israelis in the near future. "We will consider it, but the decision is that of doctors and experts, and not the politicians," he said.

On Saturday, the World Health Organization said the omicron variant has been detected in 89 countries, and COVID-19 cases involving the variant are doubling every 1.5 to 3 days in places with community transmission and not just infections acquired abroad.

Omicron's “substantial growth advantage” over the delta variant means it is likely to soon overtake delta as the dominant form of the virus in countries where the new variant is spreading locally, the UN health agency said.

WHO noted that omicron is spreading rapidly even in countries with high vaccination rates or where a significant proportion of the population has recovered from COVID-19.

It remains unclear if the rapid growth of omicron cases is because the variant evades existing immunity, is inherently more transmissible than previous variants, or a combination of both, WHO said.

Other major questions about omicron remain unanswered, including how effective each of the existing COVID-19 vaccines are against it. Conclusive data also does not exist yet on how ill omicron makes COVID-19 patients, the health agency said.

Health Ministry Director-General Nachman Ash has said that there is a "high probability" that a fourth shot will be recommended, "but we will have to see when." In the U.S., the CDC approved a fourth dose for immunocompromised people in October. Meanwhile, Pfizer CEO Albert Bourla has warned that a fourth vaccine may be needed to battle the new variant.

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