> No actual controlled evaluation that measured protection against the actual infection has ever found effect remotely as strong Such a study does exist: > U

> No actual controlled evaluation that measured protection against the actual infection has ever found effect remotely as strong Such a study does exist: > Upgrading face masks to filtering face piece (FFP3) respirators for healthcare workers on covid-19 wards produced a dramatic reduction in hospital acquired SARS-CoV-2 infections, according to research carried out at Addenbrooke’s Hospital in Cambridge. > Once FFP3 respirators were introduced [as opposed to simple surgical masks], the number of cases attributed to exposure on covid-19 wards dropped dramatically—in fact, our model suggests that FFP3 respirators may have cut ward based infection to zero. https://www.bmj.com/content/373/bmj.n1663 https://www.bmj.com/content/373/bmj.n1663