Israel was the fastest country to start vaccinating against COVID-19 a year ago, and last month it began offering a fourth injection of these drugs, or a second booster, to those over 60 in groups considered more vulnerable. and health personnel, and who had a high risk against the coronavirus.
The Sheba Medical Center (Israel) has now released part of the results of its study – the first in the world with data from a real vaccinated population –, which consisted of knowing the efficacy of a fourth dose of the COVID-19 vaccine against to the new omicron variant. Thus, it has indicated that, although the fourth vaccine has been shown to be effective in previous strains and increases antibodies more than after the third injection, this booster dose does not seem to protect well enough against omicron.
It was found that there were slightly fewer infections in those who received the fourth dose compared to those who had three of them
The vaccines investigated were those of the messenger RNA type, that is, those from Pfizer-BioNTech and Moderna, and they were tested in a group of 154 health workers from the center itself who received a fourth dose of Comirnaty (Pfizer), 120 who received their fourth injection of Spikevax (Modern) and a control group who were not immunized.
Specifically, these preliminary results indicate that one week after the administration of a fourth dose of Moderna, the rate of antibodies increased similarly to that found one week after the administration of a fourth dose of Pfizer. In addition, they found that two weeks after the administration of a fourth dose of Pfizer, there was a further increase in antibodies, slightly more than that measured after the first week.
Unpublished and very preliminary results
According to Regev-Yohai: “The increase observed in the level of antibodies is slightly higher than the maximum level observed after administering the booster dose: the third dose -in most cases-“. However, the professor explains that, with the data obtained: “we understand that, despite the significant increase in antibodies after the fourth vaccine, this protection is only partially effective against the omicron strain, which is relatively resistant to the vaccine”.
Regev-Yohai clarifies that “the fourth dose restores and even slightly exceeds the protection provided by the third dose. Therefore, although the vaccine we have today does not provide optimal protection against infection with the omicron strain, it is correct to continue with the vaccination campaign for populations at risk”.
Although the results are very preliminary, have not yet been published, and have only taken a short time to study, the researchers noted that there were slightly fewer infections among those who received the fourth dose and those in the control group at that had not been administered. Furthermore, they found no significant differences between those who received Moderna or Pfizer.
“I think the decision to allow the fourth vaccine to reach vulnerable populations is probably the right one. It may give some benefit, but probably not enough to support the decision to give it to the entire population,” Regev-Yochay concluded.
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