Whenever there is talk of suffering after an infection with Sars-CoV-2, warnings are given of severe courses in overweight people. On average, obese people have a harder time fighting the virus. In the journal Nature Medicine Scientists from Cambridge, Oxford and Edinburgh now show that People who are very overweight show a lower immune reaction than people of normal weight the longer the time since vaccination. Although the amount of virus-neutralizing antibodies immediately after the injection of the vaccine in overweight people is similar to that in people of normal weight, weeks later, overweight people show a poorer immune response. According to the researchers, people with obesity probably need a refresher more often.
The ability of antibodies to eliminate the virus decreases more quickly when people are overweight, writes the team, which analyzed data from 3.5 million Scots. According to this, people with a body mass index (BMI) over 40 have a 76 percent higher risk than infected people with a normal BMI (19 to 25) of suffering a severe course. A BMI increased to 30 to 39 also increases the risk, albeit more moderately.
The mean time until breakthrough infections occurred after the second vaccination was also dependent on weight. It was ten weeks for severe obesity, i.e. a BMI over 40. For obese (BMI 30 to 39) it was 15 weeks – compared to 20 weeks for people of normal weight. “The protection acquired through vaccination disappears more quickly in severe obesity,” says Aziz Sheikh from the University of Edinburgh, one of the lead authors of the study. “Our large database gives us indications of what would be appropriate vaccination intervals in the post-pandemic period.”
“The vaccine works for severe obesity, but the protection doesn’t last long.”
The British team also examined the number and function of immune cells depending on weight. Six months after the second vaccination, the concentration of antibodies was similar in overweight and normal weight people. However, the ability to effectively neutralize the virus was lower in the obese group. After half a year, 55 percent of the subjects who were very overweight no longer had any neutralization capacity – compared to twelve percent of subjects with a normal weight. “Our study underscores the extent to which obesity alters the response to vaccination and thus the risk of infection,” says Agatha van der Klaauw, the study’s first author. “We urgently need to understand how to restore immune function and thus minimize health risks.”
The scientists suspect that antibodies from obese people bind less well to the virus and therefore do not neutralize the pathogen as effectively. After the test persons had received a third vaccination against Covid-19, the resistance to the virus was restored in both overweight and normal weight people. But even in this case, immunity in obese people declined faster. “Although the effectiveness of the antibodies is also present in obesity through a booster vaccination, it is worrying that it disappears again so quickly,” says James Thaventhiran from the University of Cambridge. “The vaccine works for severe obesity, but the protection doesn’t last long.”
“Because of the exposure to body fat, the body’s defenses are compromised
Clemens Wendtner, chief physician for infectiology at the Munich Clinic Schwabing, where more than 7,000 Covid patients were treated, had to experience during the pandemic that obese patients were worse off. “It is now known from large studies that overweight patients have a threefold increased risk of having to be treated in intensive care and dying more frequently from Covid-19,” says Wendtner. “One reason is a constant subliminal inflammation in the body that constantly releases pro-inflammatory messengers.”
Fat cells from overweight people also have poorer blood supply and die earlier. “Dead fat cells have to be cleared away, immune cells concentrate on them, and T helper cells and B lymphocytes that are missing elsewhere are used to support the process,” says Wendtner. “The immune system is redirected.” Because of the additional burden, the defense against external enemies such as Sars-CoV-2 is severely impaired. Fewer immune cells are available.
In addition, immune cells die faster in obese people because they have to constantly produce messenger substances, a phenomenon known as senescence. And the antibodies are less functional because they are more biochemically altered in people with obesity. The antibody effect is therefore limited for the defense against infection and for the development of a vaccination reaction after administration of a vaccine.
“Not only with Covid-19, but also with other infections such as influenza, these phenomena mean that the immune system hardly recognizes the actual enemy,” says Wendtner. “This also applies to the immune response of obese people to vaccinations, whether against Covid-19 or influenza.” Even then, not enough B and T cells can be recruited for the vaccine response because they are otherwise occupied. The vaccination reaction is weaker, so that the vaccination protection in obese people wears off earlier.