Sorry if this should have been more obvious, but are you referring to something that I seem to remember hearing about where the groups vaccinating were supposedly taking blood samples from people being vaccinated for DNA analysis, which when the story broke would have tarnished the willingness of patients to get vaccinated?

I do apologize. It has been a long while since I even recalled seeing that in passing, and I never really thought about it at the time; but it has stuck with me as a case illustrating the criticality of trust in medicine.