In late February, Claire DiYenno opened her inbox to discover the golden ticket: an email from her doctor’s office with a subject line telling her that she was now eligible to get the coronavirus vaccine. It was welcome news, but unexpected.

“I was trying to think of all the different things that maybe I could have been eligible for, because I have migraines. I’ve had recent surgery,” says DiYenno, who lives in Upstate New York.

Then she opened the email and found out the real reason: Her body mass index, or BMI, was considered to be in the “obese” category.

“It was kind of like, shot-and-chaser,” she says. “Like, oh, here’s this great thing, that I’m eligible to get the vaccine, but the fact that it’s because I’m fat — I didn’t know how I felt about it.”

There are a lot of ways for people in the obese/eligible category to feel about it: Grateful to be getting the vaccine. Resentful that BMI — long known to be a flawed measurement of health — is the reason. Ambivalent about fatphobia in medicine working in their favor, for once.

As states move into broader phases of vaccine distribution, some have expanded their eligibility pool to include people suffering from various illnesses — as well as those who smoke, or who are considered to be obese according to BMI. At least 29 states have named obesity an eligible condition.

BMI was introduced in the early 19th century by a Belgian mathematician named Lambert Adolphe Jacques Quetelet. You can easily figure out your own: Plug in a height and weight to the mathematical formula, and any result over 30 is classified as obese according to the Centers for Disease Control and Prevention. For example, a 5-foot-10-inch man who weighs 210 pounds would be just over the cusp, at 30.1. (People with a BMI of 25 to 29 are “overweight,” per the chart.)

The measurement was actuarial, intended to assess the average size of men across a population; Quetlet, who was not a doctor, did not intend for it to be a measure of an individual’s health. His chart, and thus what was considered average, was developed using measurements of White bodies only. It does not take into account other factors that can contribute to weight, including muscle and bone density, which is why athletes often have high BMIs despite being in good shape. (Most of the Washington Football Team’s linebacker corps is technically obese.) A 2004 study in the American Journal of Clinical Nutrition found that waist circumference was a better predictor of health risk than BMI.

“BMI is not perfect, but it’s easy to measure,” says Dariush Mozaffarian, a cardiologist and dean at the Tufts Friedman School of Nutrition Science and Policy in Boston. “It’s reproducible, and on average it works well.”

And when it comes to covid, some doctors have seen a link between high BMI and more severe cases that require hospitalization. Mozaffarian’s latest research indicates that 30 percent of covid-19 hospitalizations were attributable to obesity. In the early days of the pandemic, when rationing equipment was a concern, obesity was among the factors that could determine whether a patient received a ventilator in some states.

However, a recent study in the Journal of Obesity found that a higher BMI was not a factor that led to different outcomes for covid-19 patients who required a mechanical ventilator.

Even before the pandemic, activists were concerned about how people with obesity are seen and treated by the medical profession.

“Fat people have been abused in medicalized spaces for a very long time,” says Darci Thoune, an English professor at the University of Wisconsin at LaCrosse who specializes in fat studies and co-authors the blog Two Fat Professors. “It only reinforces a culture of shame and contributes to the well-documented mental health issues that a lot of fat people have because of, essentially, institutionalized weight stigma.” Those issues are compounded for people of color, says Thoune, when fatphobia meets health-care discrimination.

(A note on language: Thoune prefers the word “fat,” which she and many activists feel is more empowering than “obese,” though opinions vary within the community on how to self-identify. Some prefer the term “person with obesity.”)

The obesity classification is now giving people a perceived advantage when it comes to vaccine access. It’s not a real advantage, many point out, because they still face discrimination for the way their bodies look.

“It has never been easy to exist in a plus-sized body in America. We have been ridiculed our entire existence,” says Tess Holliday, a 35-year-old model who has been featured in Vogue Italia, Nylon, and on the cover of Cosmopolitan U.K. “So honestly, if the upside of me dealing with the torment and torture because of my size my entire life means that I can get a lifesaving vaccine sooner, then cool.”

The vaccine rollout itself has illustrated the flaws of BMI as a metric. The BBC reported that a British man was offered a vaccine appointment after medical records listed him as having a BMI of 28,000, which apparently didn’t raise any alarms (a clerical error had recorded his 6-foot-2 height as 6.2 cm; he declined the appointment and is waiting his turn). And because muscle weighs more than fat, weightlifters and crossfitters with high BMIs are eligible for their shots even though they are not high risk.

Some people who aren’t eligible have been making jokes about wanting to gain “the covid 19” to get appointments. “Damn i gotta chub up,” one Twitter user responded to a Washington Post story about people with obesity being eligible for the vaccine in D.C.

“I find it really ironic that there’s so many people online joking about how they’re hoping to gain a pound or two so that their BMI reaches the level that they needed to in order to be vaccinated,” says Holliday. “No one ever takes plus-size folks’ health seriously.”

Some people who are eligible for their BMI have been reluctant to get the vaccine because they fear they will be judged. There’s a derogatory trope that people with larger bodies don’t “deserve” the vaccine because of stereotypes that weight is a result of personal choices, rather than a complicated mix of factors including genetics, their environment and mental health.

Blake McCoy, a FOX5 DC anchor, was suspended for a fatphobic tweet he made about the vaccine on Feb. 23.

“I’m annoyed obese people of all ages get priority vaccine access before all essential workers,” tweeted McCoy. “When most stayed home, we went to work everyday last March, April, May and everyday since putting ourselves & loved ones at risk.”

Followers pointed out that McCoy had anchored his show from home for periods in March and August, and had posted photos of himself traveling throughout the pandemic. He was later suspended, and tweeted a statement: “I Tweeted something insensitive and offensive. I truly regret my words and want to apologize.” McCoy declined to comment for this story.

“It’s like you don’t even think of us as people,” says Andrea Pendergast, a 34-year-old communications specialist in Richfield, Minn., of the critics. “You just think this is like, we’re cashing in a fat ticket or something. Finally, like this has been the grand plan the whole time: be fat and then we get special treatment, or something. As a fat person, we get no special treatment.”

After Kelly Jenkins posted that she was getting vaccinated, people started asking her how she was eligible. (Note: Don’t ask people this! It’s none of your business.)

“Sometimes I just say I have a comorbidity because I feel like there’s a lot more judgment in BMI than like, asthma,” says the 33-year-old Brooklyn resident.

Thoune plans to wait for her vaccine, even though she is currently eligible.

“I didn’t really want to buy into the medicalized narrative about my body as somehow being more at risk . . . to endorse the fatphobic ideas that are built into modern medicine,” she says. “That being said, I understand why other people would choose it for themselves.”

Mozaffarian says his research indicates that the BMI eligibility is appropriate.

“Obesity is clearly an independent risk factor for both severe illness, hospitalization and death, and diabetes and hypertension and are also independent risk factors on top of that,” he says. “We should absolutely be vaccinating people who are at higher risk of hospitalization and death, because that’s what we are trying to prevent.”

In practice, taking advantage of the BMI allowance can be fraught with guilt and shame. Some people might feel so embarrassed by their BMI that they don’t register for their appointments. People with high BMIs but good health — who don’t have hypertension, diabetes or any other comorbidities — might feel guilty that they’re getting opportunities that could benefit others more.

DiYenno, the Upstate New York woman who was surprised to learn she was eligible by email, says she is grateful for the chance at a dose of vaccine but ultimately disagrees with the policy.

“My mom hasn’t even been able to get it,” she says. “Granted, she lives in Ohio, but it does feel weird that I’m able to get it before she can.”

She was able to resolve some of her complicated feelings. It has been empowering for her to tell people that she got vaccinated, and she hopes BMI won’t hold others back from getting their jabs.

“If that’s all you’re going to see me as, and you’re just constantly going to lump me into this group as, ‘Ok, you’re fat, and that’s why you have all these problems,’ ” says DiYenno, “Well, in this one instance, I’ll take advantage of it.”

Correction: An earlier version of this story incorrectly stated that Andrea Pendergast lives in Ridgefield, Minn. She lives in Richfield, Minn.