NEW YORK — Before posting a selfie with her COVID-19 vaccination card on Twitter, Aditi Juneja debated whether to include an explanation for why she was eligible for a shot. “The first draft of the tweet had an explanation,” says Juneja, a 30-year-old lawyer in New York City. After some thought, she decided to leave out that her body mass index is considered obese, putting her at higher risk of serious illness if infected.