For a world crippled 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 a devastating epidemic that preceded COVID-19: obesity.
Scientists know that vaccines designed to protect the public against influenza, hepatitis B, tetanus and rabies may be less effective in obese adults than in the general population, making them more vulnerable to infection and disease. There’s not much reason to believe, obesity researchers say that COVID-19 vaccines will be something else.
“Will we have a COVID vaccine adapted to obesity next year? No way,” said Raz Shaikh, an associate professor of nutrition at the University of North Carolina-Chapel Hill.
“Will it still work in obese? Our prediction is no.”
More than 107 million American adults are obese, and their ability to work safely back, provide for their families, and restore daily life could be curtailed if the coronavirus vaccine provides them with low immunity.
In March, early in the global pandemic, a little-known study from China found that heavier Chinese patients, affected by COVID-19, were more likely to die than slimmer, suggesting a dangerous future awaited the US, whose population below the heaviest is in the world.
And then came that future.
As intensive care units in New York, New Jersey, and elsewhere filled with patients, the federal Centers for Disease Control and Prevention warned that obese people with a body mass index of 40 or more – known as morbid obesity or about 100 pounds overweight – were among the groups most at risk of becoming seriously ill with COVID-19. About 9% of American adults are in that category.
As weeks passed and a clearer picture of who was hospitalized came into focus, federal health officials extended their warning to include people with a body mass index of 30 or more. That expanded the ranks of those considered vulnerable to the most severe cases of infection to 42.4% of American adults.
Obesity has long been known to be a major risk factor for dying from cardiovascular disease and cancer. But scientists in the emerging field of immunometabolism find obesity also interests the body’s immune response, making obese people at greater risk of infection with pathogens such as the flu and the new coronavirus. In the case of influenza, obesity has emerged as a factor making it more difficult for adults to vaccinate against infection. The question is whether that applies to COVID-19.
A healthy immune system switches inflammation on and off as needed, raises white blood cells and sends proteins to fight infection. Vaccines use that inflammatory response. But blood tests show that obese people and people with related metabolic risk factors such as high blood pressure and elevated blood sugar levels experience a state of chronic mild inflammation; the inflammation turns on and stays on.
Adipose tissue – like fat – in the abdomen, liver and other organs is not inert; it contains special cells that send molecules, such as the hormone leptin, that scientists suspect induces this chronic condition of inflammation. While the exact biological mechanisms are still being investigated, chronic inflammation seems to be of interest to the immune response to vaccines, possibly overweight people subject to preventable diseases, even after vaccination.
An effective vaccine burns a controlled burn in the body, searing in cellular memory a mock invasion that never really happened.
Evidence that obese people have a blunt response to common vaccines was first observed in 1985 when obese hospital staff receiving the hepatitis B vaccine experienced a significant decrease in protection 11 months later that was not observed in non-obese people. employees. The finding was replicated in a follow-up study that used longer needles to ensure that the vaccine was injected into muscle and not fat.
Researchers have found similar problems with the hepatitis A vaccine, and other studies have found significant decreases in the antibody protection caused by tetanus and rabies vaccines in obese people.
“Obesity is a serious global problem, and the suboptimal vaccine-induced immune responses observed in the obese population cannot be ignored,” pleaded researchers from the Mayo Clinic’s 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 flu vaccine that contains many more flu virus antigens to boost their immune response.
In contrast, the diminished protection of the obese population – both adults and children – has been largely ignored.
“I’m not entirely sure why the effectiveness of vaccines in this population is no longer well reported,” said Catherine Andersen, an assistant professor of biology at Fairfield University who studies obesity and metabolic diseases. “There is a missed opportunity for greater public health intervention.”
In 2017, scientists at UNC-Chapel Hill provided a critical indication of the limitations of influenza impact. In a paper published in the International Journal of Obesity, they showed for the first time that vaccinated obese adults were twice as likely as adults of a healthy weight to develop flu or flu-like illness.
Interestingly, they found that adults with obesity produced a protective level of antibodies against the influence of flu, but they still responded poorly.
“That was the mystery,” said Chad Petit, a flu virologist at the University of Alabama.
One hypothesis, Petit said, is that obesity can trigger a metabolic dysregulation of T cells, white blood cells that are critical for the immune response. “It’s not redundant,” said Petit, who is researching COVID-19 in obese patients. “We can design better faxes that can overcome this discrepancy.”
Historically, people with high BMIs have often been excluded from drug testing because they often have related chronic conditions that can mask the results. The clinical trials that are underway to test the safety and efficacy of a coronavirus vaccine do not exclude BMI and will include people with obesity, said Dr. Larry Corey, of the Fred Hutchinson Cancer Research Center, overseeing Phase 3 trials sponsored by the National Institutes of Health.
Although trial coordinators are not specifically focused on obesity as a potential complication, Corey said, participants’ BMI will be documented and results evaluated.
Dr. Timothy Garvey, an endocrinologist and director of diabetes research at the University of Alabama, was among those who stressed that, despite the suffering questions, it is even safer for obese people to be vaccinated than not.
“The flu vaccine still works in patients with obesity, but just not as well,” Garvey said. “We still want them to be vaccinated.”
