COVID Antibodies Wane Six Months After Second Shot – Except Among One Group

Study of 5,000 Israeli hospital workers aimed to obtain a better understanding of the process in which COVID antibodies wane

Ido Efrati
Ido Efrati
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A medical worker draws a dose of the coronavirus vaccine in Jeruaslem, last month.
A medical worker draws a dose of the coronavirus vaccine in Jeruaslem, last month.Credit: Ohad Zwigenberg
Ido Efrati
Ido Efrati

An Israeli study conducted on 5,000 people indicates a steady waning of antibodies against the coronavirus six months after the second dose of the vaccine – except for one group: people who are overweight.

The study was carried out on employees of Israel’s Sheba Medical Center at Tel Hashomer and published on Wednesday by The New England Journal of Medicine.

“We’ve actually discovered from overweight people who have been vaccinated, whom we know are at increased risk of serious illness, that they surprisingly maintain a relatively high level of neutralizing antibodies over time,” Prof. Gili Regev-Yochay, who directs Sheba’s infectious disease unit. “What’s the significance of this? Of course, we need to clarify it. Are they really protected? That’s a very big question mark, and it could be that they’re not.”

The aim of the study was to try to obtain a better understanding of the process in which the antibodies wane, and try to identify the precise threshold that distinguishes when someone is protected and when they are not.

“Around the world, they are trying at the moment to identify the critical threshold of antibodies to prevent infection, illness, serious illness and even death. Identifying population groups under various thresholds, as was done in the study, will over time make it possible to estimate the level of risk of illness for every such group and thereby estimate the need, on one hand, for a booster shot, and on the other, for non-pharmacological means, such as quarantines or testing,” Regev-Yochay said.

Inside the coronavirus ward at Shaare Zedek Medical Center, Jerusalem, Tuesday.Credit: Emil Salman

A prior study directed by Regev-Yochay that was a published in The New England Journal of Medicine in July found a link between waning antibodies among vaccinated individuals and risk of illness. The current study continues in the same direction. In the new study, the roughly 5,000 employees from Sheba were given antibody blood tests once a month to track their level of antibodies following their second dose of the vaccine against COVID-19.

The findings showed that over the course of the six months following the second shot, there was a persistent, significant decline in both the level of IgG antibodies (which appear about two weeks after the vaccination and are responsible, among other things, for creating a memory of the vaccine in the body) as well as the level of neutralizing antibodies capable of preventing the virus attaching itself to cells and invading them, which apparently plays a central role in preventing disease. It was also found that the levels of the neutralizing antibodies initially dropped sharply, but then more moderately beginning with the third month following the second dose.

“We are seeing that in every age group, there is a drop, and if we’re asked whether that justifies giving young people a third dose [a booster shot], the answer is yes,” Regev-Yochay remarked.

Based on the findings, the chance of a healthy woman between the ages of 18 and 45 having no neutralizing capacity at all after six months is 2.5 percent, on average. The figure rises to 5 percent for women between 45 and 65 and to 6 percent among those 65 and over. The rate among healthy men is higher – 4 percent for men between the age of 18 and 45, 11 percent for those between 45 and 65 and 15 percent for men over 65.

On the other hand, among patients with compromised immune systems, the risk of being left without any antibodies and without the ability to neutralize the virus after six months rises to 50 percent among men 65 and over. For women with compromised immune systems, the figure is 30 percent. Among younger patients – between 45 and 65 years old – with depressed immunity, the comparable figure was 44 percent for men and 28 percent for women. In the 18-to-45 age group, it was 24 percent for men and 18 percent for women.

“We managed to build a model that presents the prospect of various populations to be at various levels of antibodies – for example older men with compromised immunity who had low levels of antibodies. According to the model that we developed, in the future we will be able to try to estimate the chance of serious or mild illness among various populations and to decide the nature of necessary treatment accordingly,” Yochay-Regev explained.

“The findings of the study have particularly special significance for countries around the world that have not yet begun giving the booster shot, or countries where about half a year has elapsed since the second dose of the vaccine. We have already begun the next stage of the study and are monitoring the dynamics of antibody levels following the booster shot,” she said. Those figures, she added, are expected to play a considerable role in deciding vaccination policy in the future.

Additional study examines myocarditis cases

Another Israeli study that was published in the New England Journal of Medicine examined cases from the beginning 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 Health Ministry employees, including the head of public health services, Sharon Alroy-Preis, and researchers from 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 Health Ministry found 304 cases of myocarditis during this period, 142 of which developed near the time of vaccination. There were 101 cases in which the patients were not vaccinated. The rest of the cases are of vaccinated patients whose condition was not believed to be related to the shot, as well as reports that were discovered to be incorrect.

The researchers examined 136 cases of myocarditis in vaccinated patients, a vast majority of whom were hospitalized for a short time with mild symptoms that went away after a few days. One patient died.

The researchers estimate that one out of every 26,000 vaccinated men in all age groups is at risk of developing myocarditis, while one out of every 218,000 women are at risk. The most at-risk group are men and women between the ages of 16–19. In this group, one out every 6,637 men and boys and one out of every 99,853 women and girls developed the condition.

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