I see people say "why is there so much resistance to doing vaccinated vs. unvaccinated studies?" like the Henry Ford "Inconvenient" study.
The reasons "any vs. no vaccine" studies are problematic have nothing to do with any "resistance" — they reflect genuine methodological limitations. The completely unvaccinated cohort is typically small and differs from the vaccinated population in so many systematic ways that isolating causal vaccine effects becomes nearly impossible. That's why most researchers focus on more tractable questions: specific vaccines, different schedules, timing of events relative to vaccination, and dose-response relationships. It is not "resistance", it is an attempt to do good science.
There's a contingent that treats long-term saline placebo-controlled RCTs (possibly of all vs. no vaccines) as the only legitimate study design for assessing vaccine safety, and assumes the reason they aren't done is that researchers fear what they'd find. But this ignores the practical reality: no one advancing that argument has ever proposed a workable design, and if they tried, they'd quickly discover why it's infeasible. Even if such a trial were somehow conducted, it couldn't detect rare events, and its findings would still be constrained by whatever schedule was used in the active arm.
The same people advocate for "any vs. no vaccine" observational designs as the gold standard retrospective alternative — again implying the only barrier is fear of results. But well-known biases and confounders make these designs deeply problematic, and the versions typically promoted fail to adjust for them, dramatically overclaim the strength of their conclusions, and refuse to acknowledge fundamental limitations.
Most tellingly, this group dismisses the entire existing safety literature because it doesn't meet their preferred design criteria — effectively pretending no safety data exists. In doing so, they ignore the largest and most rigorous studies available, which happen not to support their conclusions.