Stanford Medicine Long COVID Study Blows Up Because of Unmasked Staff https://www.thedailybeast.com/stanford-medicine-long-covid-study-blows-up-because-of-unmasked-staff
It could be argued that it also invalidated the study, in that it introduced variable, uncontrolled exposure willy-nilly to the subjects, rendering subsequent observations meaningless. So unethical *and* just plain bad science.