After the fourth COVID vaccination, the level of antibodies increased, but not enough to prevent infection with Omicron.

According to preliminary findings from a study of 150 healthcare professionals done at the Sheba Medical Center, the fourth dose of the Pfizer coronavirus vaccine raises antibody levels in the blood but does not appear to provide protection against infection by the coronavirus Omicron type.

“Two weeks after administering the fourth vaccine, we see a good increase in the antibodies, higher than after the third dose, but not high enough against Omicron,” says lead researcher Prof. Gili Regev-Yochay.

“People are getting infected, maybe in slightly lower numbers compared to individuals in the control group, but not lower in any significant way.”

On December 27, Sheba began a clinical trial to assess the safety and efficacy of a fourth shot of Pfizer vaccine, providing the vaccine to 150 healthy employees who had been boosted at least four months prior. They all got a serological result of less than 700, indicating that they no longer had enough antibodies to guard against the Omicron variant.

Regev-Yochay previously stated that the antibody level grew five-fold a week after the jab, which she regarded as a good outcome but not as good as they had hoped for because the result was similar to the third dose and not greater.

“This is not what you expect from a booster,” this is what she said earlier.

Regev-Yochay stated seven days later that while the number of antibodies had increased, it did not appear to be enough to combat Omicron’s infectiousness.

“By now, we know that the level of antibodies needed to be protected from Omicron is probably too high for this vaccine, even if it is a good vaccine,” she added.

Sheba’s researchers are also performing an identical study, giving another set of 150 healthy hospital staff the fourth dose of Moderna’s vaccine.

In this case, too, the antibody level climbed a week after the new booster to a level similar to that recorded after the Pfizer vaccine, according to Regev-Yochay.

“These are very preliminary results, before any publication,” she said.

“But we decided to share them because we understand the urgency of the public to receive information.”

Regev-Yochay declined to provide the number of infections or antibody levels, stating that the researchers would do so after more investigation.

She also backed Israel’s choice to administer the fourth vaccine to people over 60 and those in high-risk groups.

“I think that the decision to allow a fourth vaccine for the vulnerable populations is probably correct,” she said.

“It may offer some benefits, although probably not enough to support the notion of offering it to all of the population.”

More than 550,000 adults aged 60 and up have gotten the vaccine in the last two weeks.

Vaccine efficacy is measured in more than just the ability to prevent infection. The ability to avert major symptoms is the other.

Regev-Yochay stated that it was too early to determine the impact of the fourth shot on serious disease at this time.

Image Credit: Getty

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