This story was produced by Kaiser Health News, an editorially independent program of the Kaiser Family Foundation.

For a world crippled by the coronavirus, salvation hinges 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 vexing epidemic that long preceded COVID-19: obesity.

Scientists know that vaccines engineered to protect the public from influenza, hepatitis B, tetanus and rabies can be less effective in obese adults than in the general population, leaving them more vulnerable to infection and illness. There is little reason to believe, obesity researchers say, that COVID-19 vaccines will be any different.

“Will we have a COVID vaccine next year tailored to the obese? No way,” said Raz Shaikh, an associate professor of nutrition at the University of North Carolina-Chapel Hill.

“Will it still work in the obese? Our prediction is no.”

More than 107 million American adults are obese, and their ability to return safely to work, care for their families and resume daily life […]