Thread by @MikeAlbertMD

1/ "MASK"ING THE CASE: WHY THERE SHOULD BE A UNIVERSAL MASK MANDATE

I have been fascinated by the discussion around mask use during the pandemic. Suffice it to say, the US' compliance has not been great considering the size of the current outbreak across the US states. [thread]

2/In fact, as recently as July 2020, there was a only ~48% chance everyone would be masked during five random public encounters.

original article: nytimes.com/interactive/20…

3/So why all the lack of compliance with mask use? Do masks really reduce the risk of COVID19 transmission? Let us jump in...[thread]

4/ For starters, one needs to go back to Jan-March 2020, at the time, the @CDC and @WHO, after reviewing the evidence for #SARSCoV2, felt that there was insufficient evidence to recommend the use of masks to limit community spread.

factcheck.org/2020/05/outdat…

5/ During the early months of the pandemic, several public officials made statements in support of the institutional positions. This all changed on April 4th, when the CDC reversed their position in light of developing evidence. cdc.gov/coronavirus/20…

7/Despite the reversal (due to the evolving body of evidence), many people felt they were lied to, and the polarization around face masks became more apparent with the continued politicization of the public health measure: vox.com/2020/7/21/2133…

7/Ok, so what does the evidence suggest? Do masks reduce YOUR RISK of getting #COVID19?

While the direct evidence is somewhat limited (given the recency of the pandemic), the indirect evidence is clear and there is a growing corpus of direct evidence supporting the use of masks.

8/ The CDC has published several case studies over the last few months.

1⃣During an outbreak on USS Theodore Roosevelt, navy service-men who self-reported wearing masks had 70% decreased odds of infection (OR 0.3, 95% CI 0.2-0.5). cdc.gov/mmwr/volumes/6…

9/
2⃣ Also, who can forget the 2 COVID19+ hair stylists in Springfield, MO. They took care of 139 clients over an 8-day period. There were ZERO reports of secondary infection on f/u. Difference? Both stylists and clients wore masks throughout every encounter.

9.5/ Don't forget the Georgia Summer Camp! While staff members were REQUIRED to wear cloth masks, campers were NOT. Test results were available for 344 (58%) attendees; among these, 260 (76%) were positive. The overall attack rate was 44% (260 of 597). cdc.gov/mmwr/volumes/6…

10/ A retrospective cohort study from Beijing, China found that mask use of any kind within households was found to decrease odds of secondary infection by 79% (aOR 0.21, 95% CI 0.06-0.79). ncbi.nlm.nih.gov/pmc/articles/P…

11/ How about in the US? Leyu and Wehby 2020 analyzed the infection growth rates across all US states around the time of state-wide mandate. They wanted to assess the impact of state-wide mandates on county-level case growth.

12/ What they found: daily COVID19 growth rates declined by 0.9, 1.1, 1.4, 1.7, and 2.0 percentage points in 1-5, 6-10, 11-15, 16-20, and 21 or more days away from the mandate. Conversely, states that did implement a mask mandate experience continued positive growth in new cases.

13/ Zhang et al., 2020 compared responses across 3 epicenters for disease: China, Italy, and NYC. What they found is that all three locations employed mitigation strategies (effectively to various degrees) early: social distancing, testing, tracing, quarantine, and isolation.

14/ Only China, who was able to institute mask policies early flattened their curve. Both Italy and NYC experienced linear growth in new cases prior to mask mandates: April 6th and April 17th for Lombard, Italy and NYC, respectively.

15/Only after mask mandates did their curves start to flatten. By their estimates, the number of infections were reduced by 78,000 in Italy (April 6th – May 8th) and 66,000 in NYC (April 17th – May 9th) from what was expected. NYC decreased their rate of growth by 3% daily.

16/ How about for HCWs? One retrospective cohort study showed that of HCWs who wore n95s (N=278) at the time of the outbreak in China, none were infected despite having a higher risk of exposure (odds ratio 8.33). Conversely, 10/213 HCWs who did not wear masks were infected.

17/ Most of the other evidence (higher level of evidence) is indirect and extrapolated from other epidemics: SARS, MERS, and influenza. Iannone et al., 2020 conducted a meta-analysis, which showed that N95 use (versus mask) avoided 73 respiratory infections per 1000 HCWs.

18/ Bartoszko et al., 2020 found no difference in the reduction of viral respiratory infections or clinical respiratory infections when healthcare workers used N95s versus surgical masks (N95 ORs: 1.06, 95% CI (0.9-1.25) and 1.49, 95% CI (0.98-2.25), respectively.

19/ The seminal meta-analysis by Chu et al., 2020 as supported by WHO reinforces the common theme. Whether unadjusted or adjusted by estimates, and despite setting (HC vs community), face masks result in a large reduction in odds (risk) of infection (aOR 0·15, CI 0·07 to 0·34).

20/ For HCWs, N95s or similar respirators over surgical masks likely provide a further reduction in risk, although finding is inconsistent.

21/ So where does this leave us? Skeptics will say there are no RCTs for #COVID19, and they are right; however, the corpus of evidence, including the indirect data and the new obs data for SARS-CoV-2, suggest a consistent & significant ⬇️ in the risk of infxn by wearing a mask.

22/ I believe the evidence is clear that universal mask policies work in addition to other mitigation and containment strategies, and they should be mandated across the US and the rest of the world so long as the virus remains active. #WearAMaskSaveYourLife [END]

Reference for #16: journalofhospitalinfection.com/article/S0195-…