> 2020 was that there is no evidence that masks are effective, at all, against the spread of infectious diseases. No. The claim was that masks were effective

> 2020 was that there is no evidence that masks are effective, at all, against the spread of infectious diseases. No. The claim was that masks were effective only when used by trained hospital personnel, which is still true. It was not clear if they would be effective when used by non trained hospital staff, and it was also not clear if non n95 masks (like cloth masks) would be effective at all. Once it was determined that they were effective, the advisory was changed to reflect that. There was no backpedaling, only an increase in understanding which resulted in an update to guidance.