willingness to change with new evidence: vaccine quacks never change their mind in light of new evidence. They have fixed ideas that vaccines are safe and effective regardless of any evidence to the contrary

ruthless peer review: not one single study that is favorable to vaccines, has ever been retracted due to peer review. If you read the peer review feedback, it looks like low-effort blog comments. “Looks good”, “nice work”...

Takes into account all new discoveries: vaccines quacks never take into account any study that is not favorable to vaccines. They always find a reason to dismiss unfavorable studies, and/or have it retracted by any means necessary. Instead they only take into account favorable studies.

invites criticism: vaccine quacks do not invite criticism, and always dismiss any criticism as merely a conspiracy theory. Vaccine quacks can not name a single “credible” vaccine critic, because in their mind no vaccine critic can be critical.

verifiable results: the vast majority of people who get a vaccine, do not get any followup verification on efficacy or safety. Their “studies” are not able to be replicated by independent 3rd parties.

Limits claims of usefulness: vaccine quacks claim vaccines prevent not only the intended infection, but that vaccines also prevent autism, alzheimers, autoimmune diseases, SIDS, mental retardation, asthma, ...

Accurate Measurements: vaccine quacks claim vaccines have saved “millions of lives”, that adverse reaction are “very rare”, that the flu shot is “a pretty close match”... they hedge every claim with weasel words like may, might, maybe, could be, unclear, etc.