A longtime favorite technique of antivaxxers has been to do bad ecological studies to imply that vaccines cause harm. Why is a Harvard investigator inadvertently using the ecological fallacy the same way antivaxxers used to do before COVID-19?

A longtime favorite technique of antivaxxers has been to do bad ecological studies to imply that vaccines cause harm. Why is a Harvard investigator inadvertently using the ecological fallacy the same way antivaxxers used to do before COVID-19?