New Mask Study

Medical Masks Versus N95 Respirators for Preventing COVID-19 Among Health Care Workers. https://doi.org/10.7326/M22-1966

Professor Carl Heneghan of the Centre for Evidence Based Medicine at Oxford University has just tweeted the results of a sizeable multicentre randomised trial into mask effectiveness (29 centres, 1009 subjects). I noted that they'd done something sensible and that is to compare performance of ear loop masks (a.k.a. surgical masks) with full-on N95 respirators (proper-job PPE), so I grabbed my morning lemon tea and smacked the link in eager anticipation.

I should not have bothered for here's the rather thin conclusion:

It is uncertain if medical masks offer similar protection against COVID-19 compared with N95 respirators.

What they’re doing their best at avoiding is telling you that the primary outcome (incidence of COVID by mask type) yielded a hazard ratio (HR) of 1.14, [95%CI = 0.77 to 1.69]. When you see a hazard ratio confidence interval straddle zero like this it means one thing… the difference observed is statistically insignificant!

In plain English, a fragile and loosely worn me…