Dr. WH. Kellogg (1920)

Dr. Kellogg conducted one of the first - if not the first - study on masks following the Spanish flu (of which people died of bacterial pneumonia). While he contended poor usage and low quality materials for its construction impeded its usefulness, he nevertheless concluded masks are ineffective:

“Masks have not been demonstrated to have a degree of efficiency that would warrant their compulsory application for the checking of epidemics.”