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An Israeli study of 5,000 people shows a steady decrease in antibodies to the coronavirus six months after the second dose of the vaccine – with the exception of one group: overweight people.
The study was performed on employees of Israel’s Sheba Medical Center in Tel Hashomer and published Wednesday by the New England Journal of Medicine.
“We have actually found in overweight people who have been vaccinated, who we know are at increased risk of serious disease, that they surprisingly maintain a relatively high level of neutralizing antibodies over time,” he said. said Professor Gili Regev-Yochay, who heads Sheba’s study. infectious diseases unit. “What is the significance of this? Of course, we need to clarify this. Are they really protected? That’s a really big question mark, and they might not be.
The aim of the study was to try to better understand the process of lowering antibodies and to try to identify the precise threshold that distinguishes when someone is protected and when they are not.
“All over the world, they are now trying to identify the critical threshold of antibodies to prevent infection, disease, serious illness and even death. Identifying population groups under different thresholds, as was done in the study, will over time estimate the level of disease risk for each of these groups and thus estimate the need for on the one hand, for a recall, and on the other hand, for non-pharmacological means, such as quarantines or tests, ”said Regev-Yochay.
An earlier study led by Regev-Yochay and published in the New England Journal of Medicine in July found a link between decreased antibodies in people vaccinated and disease risk. The current study is continuing in the same direction. In the new study, Sheba’s roughly 5,000 employees underwent antibody blood tests once a month to track their antibody level after their second dose of the COVID-19 vaccine.
The results showed that during the six months following the second injection, there was a persistent and significant drop in both the level of IgG antibodies (which appear about two weeks after vaccination and are responsible, among other things, for the creation of a memory of the vaccine in the body) as well as the level of neutralizing antibodies capable of preventing the virus from attaching to and invading cells, which apparently plays a central role in preventing the disease . It was also found that the levels of neutralizing antibodies first dropped sharply, but then more moderately from the third month after the second dose.
“We see that in each age group, there is a decrease, and if we are asked if this justifies giving a third dose to young people [a booster shot], the answer is yes, ”remarked Regev-Yochay.
Based on the results, the probability that a healthy woman aged 18 to 45 will have no neutralizing ability after six months is 2.5% on average. The figure rises to 5 percent for women between 45 and 65 and 6 percent for those 65 and over. The rate in healthy men is higher – 4% for men between 18 and 45, 11% for those between 45 and 65 and 15% for men over 65.
On the other hand, in patients with weakened immune systems, the risk of being without antibodies and without the ability to neutralize the virus after six months is 50% in men 65 years and older. For women with weakened immune systems, the figure is 30 percent. Among younger patients – between 45 and 65 – with depressed immunity, the comparable figure was 44% for men and 28% for women. In the 18 to 45 age group, it was 24% for men and 18% for women.
“We were able to build a model that presents the perspective of diverse populations of being at different levels of antibodies – eg older men with compromised immunity who had low levels of antibodies. According to the model that we have developed, in the future we will be able to try to estimate the risk of severe or mild disease among different populations and decide on the nature of the treatment needed accordingly ”, explained Yochay- Regev.
“The study results are of particular importance for countries around the world that have yet to start the booster, or countries where about six months have passed since the second dose of the vaccine. We have already started the next stage of the study and are monitoring the dynamics of antibody levels after the booster, ”she said. These numbers, she added, are expected to play a huge role in deciding immunization policy in the future.
Additional study examines cases of myocarditis
Another Israeli study published in the New England Journal of Medicine looked at cases from the start of the COVID vaccination campaign in December 2020 until the end of May, in which patients who received the vaccine suffered from myocarditis.
The study was conducted by employees of the Department of Health, including the chief of public health services, Sharon Alroy-Preis, and researchers at Hadassah University Hospital and other medical institutions in the country.
Between December and May, 5.4 million people in Israel were vaccinated with the first dose and 5.1 million received the second. The Department of Health found 304 cases of myocarditis during this period, 142 of which developed at the time of vaccination. There were 101 cases in which the patients were not vaccinated. The remainder of the cases involve vaccinated patients whose condition was not believed to be related to the gunshot, as well as reports that turned out to be incorrect.
The researchers looked at 136 cases of myocarditis in vaccinated patients, a large majority of whom were hospitalized for a short time with mild symptoms that resolved after a few days. One patient died.
Researchers estimate that one in 26,000 vaccinated men in all age groups is at risk of developing myocarditis, while one in 218,000 women is at risk. The most at-risk group are men and women aged 16-19. In this group, one in 6,637 men and boys and one in 99,853 women and girls developed the disease.
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