>> I read that shields have almost no effect at all at preventing the virus from
>> being passed to other people or preventing you from getting it. You are probably better
>> protected wearing glasses and a good mask.
I doubt if anyone has done a controlled trial, or even an observational one, only thought experiments. Assumptions have presumably been made about how much a visor could reduce airborne virus cf. masks or nothing. So our opinions are probably nearly as valid as those of "experts" on this one.
Clearly they don't prevent the wearer breathing out the virus and it seems likely that less of it will be captured than would be by even a simple face mask. But it would stop the wearer literally spitting virus around when speaking/breathing/coughing so even if a third party still comes into contact with the virus they are likely to receive less of it.
I think some of the observational work on mask wearing has suggested that there is a worthwhile reduction in viral loads with masks which correlates with milder illness - I can't cite anything so maybe I read too much into it, but it would make sense.
Where people claim exemption from masks I have a but more sympathy if they wear a visor. One of the volunteers I work with uses a visor as she struggles with a mask and I feel reasonably happy with that especially as she is very voluble!
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