Thread by @jeffgilchrist

COVID-19: Impact of mask usage and mandates

This thread explores what kind of measured impact mask usage and mandates have actually had in schools and with healthcare workers. TLDR: They substantially reduce infections and outbreaks. #FASSST #LongCovidKids #onted 🧵1/

Healthcare workers are exposing themselves to pathogens every day. Most are just given surgical masks which are not designed to protect against aerosol transmission and have historical reasons for not recognizing this ( onlinelibrary.wiley.com/doi/10.1111/in… ). H/T: @jljcolorado 2/

A new publication looking at 2919 healthcare workers (HCW) with frequent COVID-19 patient exposure found high quality respirators (e.g. N95/FFP2) substantially reduced COVID-19 infections compared to surgical masks ( jamanetwork.com/journals/jaman… ). H/T: @EricTopol 2/

Of the HCWs in the study, 749 (26%) were infected with COVID-19 while positivity was 13% in HCWs without patient exposure. For HCW exposed to patients, positivity was 21% for those using respirators and 35% for using surgical/mixed masks. 3/

"The odds of being COVID-19 positive were reduced by more than 40% in individuals using respirators, irrespective of cumulative exposure, even after adjusting for multiple work and non-work related covariables." 4/

The graph shows an interesting trend of COVID-19 positivity in HCWs depending on cumulative patient exposure and mask type. You can see that positivity in HCWs wearing only surgical masks only or mixed keeps increasing the longer the exposure. 5/

At more than 64 hours of cumulative exposure, the surgical mask/mixed group had more than 55% positivity while the respirator only group was around 30% positivity. 6/

Another study looking at schools in Greater-Boston Area School Districts found that no mask requirement means kids miss school ( medrxiv.org/content/10.110… ).

@OttCatholicSB @OCDSB @ecolecatholique @MonCepeo @OPCouncil @ETFOeducators @osstf @OFLabour #FASSST #COVIDisAirborne 7/

Lifting school masking requirements was associated with an estimated additional 45 COVID-19 cases per 1,000 students, representing about 30% of all cases observed in schools during the time frame studied. For school staff it was even worse, an extra 81.7 cases per 1,000. 8/

"If all students who tested positive followed state guidelines to isolate for 5+ days, that's almost 20,000 *extra* missed school days!" (

https://twitter.com/EpiEllie/status/1557399505728937987

). 9/

The school districts that dropped mask requirements were also the ones who had better budgets, better buildings, better vaccination rates, and lower community COVID-19 levels but it wasn't enough to allow dropping mask mandates to work. 10/

The researchers conclude that "Masking is a relatively low-cost but effective intervention that can protect students and staff from substantial illness and loss of in-person days in school." 11/

The province of Alberta also found using their own data that schools without mask mandates had 3.2x more outbreaks in those schools on average (

https://twitter.com/jeffgilchrist/status/1552268219792195585

| facebook.com/jeff.gilchrist… ). 12/

Mask mandates reduced outbreaks by 68% in Alberta schools but the province buried their own analysis and it took a court-order to make the information available. 13/

Not only that, but there are more cases in the communities surrounding schools than the average across the whole city of Edmonton so they knew that cases are being spread from schools to communities and recorded each wave has increased the risk of child hospitalization. 14/

But are you worried that kids wearing masks at school might harm their language development? Thankfully the American Academy of Pediatrics provides some information for parents, that there is no evidence of harm (

https://twitter.com/AmerAcadPeds/status/1563241280741994496

). 15/

Research has also shown, "wearing a mask in school does not hinder a young child’s ability to learn language, even if they have hearing loss" ( news.miami.edu/stories/2021/0… ). H/T: @DataDrivenMD 16/

On the other hand research has also shown that "trouble remembering or concentrating" are common symptoms among children suffering from Long COVID ( thelancet.com/journals/lanch… ) and ( medicalnewstoday.com/articles/how-c… ). H/T: @DataDrivenMD 17/