This article has been revised to reflect the following correction: Because of an editing error, an earlier version of this article misstated the name of an institution. It is the University of Texas Southwestern Medical Center, not Southwestern Medical Center.
More than two months after he was fully vaccinated against Covid, a doctor in New York woke up with a headache and a dull, heavy feeling of fatigue. A fever and chills soon followed, and his senses of taste and smell began to fade.
This, he thought, could not be happening. But it was: He tested positive for the coronavirus.