John Barthelow Classen is an American immunologist and opponent of vaccination.[1] He received his M.D. from the University of Maryland, Baltimore in 1988, his M.B.A. from Columbia University in 1992 and obtained his medical license in October 1997.[2][3] He is best known for publishing research concluding that vaccines, in particular the Hib vaccine, cause insulin-dependent diabetes mellitus,[4] a hypothesis he proposed based on experiments he conducted on mice in 1996.[5] His views are disputed and considered unverified.
A widely reposted 2021 Facebook post claiming that the mRNA vaccines against COVID-19 could cause prion diseases was based on a paper by Classen. The paper was published in Microbiology and Infectious Diseases, whose publisher, Scivision Publishers, is included in Beall's list of publishers of predatory journals. Vincent Racaniello, professor of microbiology and immunology at Columbia University, described the claim as "completely wrong".[1][6][7] Tulane University virologist Robert Garry stated that Classen has offered no evidence for the three pillars of his argument: that the sequence overlaps between the Pfizer vaccine are greater than occur with any randomly-selected stretch of RNA, or that the vaccine could cause zinc to be released and that doing so would affect its purported targets as he proposes.[8]