"but considering that nowadays even (formerly) serious scientists are suspect,"

Oh, come on already. Scientists are suspect only because a) most people are not competent and do not understand what they're saying and (b) some experts speak outside their competency, such as an MD giving his impression of vaccines. Dr. Campbell is unfortunately one of those. Vincent, a virologist who's studied the polio virus for his professional life, has discussed him, how he misstates things.

Do yourself a favor and start watching This Week in Virology (at microbe.tv/twiv) for the views of real experts in the field. Campbell has no competency in the field and that makes all the difference and leads to him making stuff up and you, not being a virologist, has no ability to determine that, so you're left believing him.