An Israeli medical study has reportedly found that although a fourth booster shot of Covid-19 vaccines may increase antibodies to even higher levels than the third dose, it is not enough to prevent Omicron-type infection.
The Israeli Sheba Medical Centre (ISMC) announced that it administered second booster doses in a clinical trial to staff and is examining the effect of the Pfizer vaccine booster dose in 154 people after two weeks and then with the Moderna booster dose in 120 people after one week.
The vaccines caused an increase in the number of antibodies "even a little higher than we had after the third dose," said Gili Regger Yohai, ISMC Director of the Communicable Diseases Unit.
However, that is probably not enough for Omicron," he told reporters. "We know by now that the level of antibodies needed to protect and prevent Omicron infection is probably much higher - too high for the vaccine, even if it is a good vaccine."
The findings, which the ISMC said were the first of its kind worldwide, are preliminary and have not yet been published.
Israel was the first country to adopt vaccinations much faster and earlier than other countries over a year ago and last month began offering second and fourth booster shots of Covid-19 vaccines to the most vulnerable high-risk groups.