Late last year, a semi-retired British scientist co-authored a petition to Europe's medicines regulator. The petitioners made a bold demand: Halt COVID-19 vaccine clinical trials. Even bolder was their argument for doing so: They speculated, without providing evidence, that the vaccines could cause infertility in women. Scientists denounced the theory. What gave the debunked claim credibility was that one of the petition's co-authors, Michael Yeadon, wasn't just any scientist. The 60-year-old is a former vice president of Pfizer. In recent months, Yeadon (pronounced Yee-don) has emerged as an unlikely hero of the so-called anti-vaxxers, whose adherents question the safety of many vaccines, including for the coronavirus. The anti-vaxxer movement has amplified Yeadon's skeptical views about COVID-19 vaccines and tests, government-mandated lockdowns and the arc of the pandemic. Yeadon has said he personally doesn't oppose the use of all vaccines. Yeadon isn't the only respected scientist to have challenged the scientific consensus on COVID-19 and expressed controversial views. Luc Montagnier, another Nobel Prize winner, said last year that he believed the coronavirus was created in a Chinese lab.