(Kaiser Health News) — For a world paralyzed by the coronavirus, salvation depends on a vaccine.
But in the United States, where at least 4.6 million people have been infected and nearly 155,000 have died, the promise of that vaccine is hampered by an epidemic that preceded Covid-19: obesity.
Scientists know that vaccines designed to protect the public from influenza, hepatitis B, tetanus, and rabies may be less effective in obese adults than in the general population, leaving them more vulnerable to infection and disease. The researchers say there is little reason to believe that COVID-19 vaccines will be different.
«Will we have a covid vaccine next year adapted to the obese? No way, ”said Raz Shaikh, associate professor of nutrition at the University of North Carolina-Chapel Hill.
«Will it continue to work in the obese? Our prediction is no.
More than 107 million American adults are obese and their ability to safely return to work, care for their families and resume daily life could be reduced if the coronavirus vaccine provides them with weak immunity.
In March, still at the start of the global pandemic, a little-known study from China found that heavier Chinese patients affected with COVID-19 were more likely to die than slimmer ones, suggesting a dangerous future that awaits. The US, whose population is among the largest in the world.
And then that future came.
Like intensive care units in New York, New Jersey, and other places full of patients, the federal Centers for Disease Control and Prevention warned that obese people with a body mass index of 40 or higher, known as morbid obesity or overweight of about 100 pounds, were among the groups most at risk of becoming seriously ill with COVID-19. About 9% of American adults are in that category.
As the weeks passed and a clearer picture of who was being hospitalized came into focus, federal health officials expanded their warning to include people with a body mass index of 30 or more. That vastly expanded the ranks of those considered vulnerable to the most severe cases of infection, to 42.4% of American adults.
Obesity interferes with the immune response
Obesity has long been known to be a significant risk factor for death from cardiovascular disease and cancer. But scientists in the emerging field of immunometabolism find that obesity also interferes with the body’s immune response, putting obese people at higher risk of infection from pathogens like influenza and the new coronavirus.
In the case of the flu, obesity has become a factor that makes it more difficult to vaccinate adults against the infection. The question is whether that will be valid for covid-19.
A healthy immune system turns inflammation on and off as needed, calling in white blood cells and sending out proteins to fight infection. Vaccines take advantage of that inflammatory response. But blood tests show that obese people and people with related metabolic risk factors, such as high blood pressure and high blood sugar, experience a state of chronic mild inflammation; the inflammation flares up and stays on.
The adipose (or fat) tissue in the abdomen, liver, and other organs is not inert; It contains specialized cells that deliver molecules, such as the hormone leptin, that scientists suspect induce this chronic state of inflammation. While the exact biological mechanisms are still being investigated, chronic inflammation appears to interfere with the immune response to vaccines, possibly subjecting obese people to preventable diseases even after vaccination.
An effective vaccine fuels controlled damage within the body, causing a simulated invasion of cell memory that never actually happened.
Evidence that obese people have a strong response to common vaccines was first seen in 1985 when obese hospital employees who received the hepatitis B vaccine showed a significant decrease in protection 11 months after it was not seen in non-obese employees. The finding was repeated in a follow-up study that used longer needles to ensure that the vaccine was injected into muscle and not fat.
Researchers found similar problems with the hepatitis A vaccine, and other studies have found significant decreases in antibody protection induced by tetanus and rabies vaccines in obese people.
“Obesity is a serious global problem, and the suboptimal vaccine-induced immune responses seen in the obese population cannot be ignored,” pleaded researchers from the Mayo Clinic Vaccine Research Group in a 2015 study published in the journal Vaccine. .
Vaccines are also known to be less effective in older adults, which is why those 65 and older receive an annual supercharged flu shot that contains many more antigens from the flu virus to help boost their immune response.
On the contrary, the diminished protection of the obese population, both adults and children, has been largely ignored.
“I’m not entirely sure why the efficacy of the vaccine in this population has not been better reported,” said Catherine Andersen, an assistant professor of biology at Fairfield University who studies obesity and metabolic diseases. “It is a missed opportunity for greater public health intervention.”
In 2017, scientists from the University of North Carolina – Chapel Hill provided a critical clue about the limitations of the flu vaccine. In an article published in the International Journal of Obesity, researchers showed for the first time that vaccinated obese adults were twice as likely to develop flu or flu-like illnesses compared to adults of a healthy weight.
Interestingly, the study found that obese adults produced a protective level of antibodies against the flu vaccine, but these adults still responded poorly.
“That was the mystery,” said Chad Petit, an influenza virologist at the University of Alabama.
Petit said that one hypothesis is that obesity may trigger a metabolic dysregulation of T cells, the white blood cells critical for the immune response. “It’s not insurmountable,” said Petit, who is researching COVID-19 in obese patients. “We can design better vaccines that can overcome this discrepancy.”
Historically, people with a high BMI have often been excluded from drug trials because they often have related chronic conditions that can mask the results. Ongoing clinical trials to evaluate the safety and efficacy of a coronavirus vaccine do not have a BMI exclusion and will include people with obesity, said Dr. Larry Corey of the Fred Hutchinson Cancer Research Center, who is overseeing the trials. of phase III sponsored by the National Institutes of Health in the United States.
Although the trial coordinators do not specifically focus on obesity as a potential complication, Corey said, the participants’ BMI will be documented and the results evaluated.
Dr. Timothy Garvey, an endocrinologist and director of diabetes research at the University of Alabama, was among those who emphasized that despite lingering questions, it is still safer for obese people to get vaccinated than if they don’t .
“The flu vaccine still works in obese patients, but not as well,” Garvey said. “We still want them to get vaccinated.”
KHN (Kaiser Health News) is a non-profit news service that covers health problems. It is an editorially independent program of KFF (Kaiser Family Foundation) that is not affiliated with Kaiser Permanente.