September 30, 2022

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Israeli Study Shows 4th Shot Less Effective against Omicron

3 min read

The results of the first major study conducted on the fourth shot of the COVID-19 vaccine are out and they do not bode well. On Monday, researchers from the Sheba Medical Center disclosed that there was a significant increase in the antibody levels after administering the fourth shot of the Pfizer vaccine. Lead researcher, Prof. Gili Regev-Yochay said that the vaccine increases or enhances the number of antibodies after two weeks, which include neutralizing antibodies. She noted that the increase was higher than what was seen after the third shot. Last week, she had reported that it increased fivefold and said that it had risen further, but did not provide any numbers.

However, she added that the rise was not enough to combat the Omicron variant, which means that the fourth dose will not deliver a lot of protection against infection from the highly-contagious variant. At-risk and the elderly people in Israel were the first population in the world to take the fourth shot and they have been waiting for an answer to understand if it makes them safer or not. While this is an answer, but it also gives rise to some important questions. The study comprises of a small number of participants, no more than 150.

These are employees at Sheba Medical Center, who had been administered the fourth shot last month. A Moderna shot had also been given to 120 people, after they had already received three shots of Pfizer. These people are also building antibodies at the same rate, but the experiment is still in its early stages. Regev-Yochay disclosed that some of the recipients of the fourth shot had suffered from infections, but antibody counts is her primary variable in the study. Her study is important because it aims to measure the effectiveness of the vaccine against the Omicron variant. 

For months, Sheba has been keeping track of a control group comprising of 6,000 people and has cross-referenced them in recent weeks with rates pertaining to the Omicron infection. According to experts, these results are not surprising because they had been expected. Prof. Cyrille Cohen, immunologist from the Bar Ilan University, said that the results of the study showed that the spike protein of the Omicron variant is different from the one included in the vaccine. He added that the study had not addressed the most important question that is the number of patients who get a severe infection. 

Cohen said that the fourth shot would help in reducing serious illness because of the Omicron variant, but it would not be the same as its effectiveness against the Delta variant. Cohen stated that even though antibodies could indicate the risk of infection, it is far more difficult to assess the vulnerability to serious infection. Cohen said that the Sheba research was important, but couldn’t provide the data needed because the overall sample size is very small, so they would not be able to come to reasonable conclusions about patients who get a severe infection and the demographic is also not appropriate. 

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