New Paper: Masks achieve nothing in terms of Spread

Written by Damian D. Guerra and Daniel J. Guerra on May 29, 2021. Posted in Current News

Image: Die Welt

Latest analysis shows yet again – yet again – what we already knew from 40 years of published research. And also empirically from simply glancing over the past year’s real-world data. Masks don’t work!

Our main finding is that mask mandates and use are not associated with lower SARS-CoV-2 spread among US states. 80% of US states mandated masks during the COVID-19 pandemic.

Mandates induced greater mask compliance but did not predict lower growth rates when community spread was low  (minima) or high (maxima). We infer that mandates likely did not affect COVID-19 case growth [15], as growth rates were similar on all days between actual or modeled issuance dates and 6 March 2021. Higher mask use (rather than mandates per se) has been argued to decrease COVID-19 growth rates [11].

While compliance varies by location and time, IHME estimates are robust (derived from multiple sources [17]) and densely sampled (day-level precision). Higher mask use did not predict lower maximum growth rates, smaller surges, or less Fall-Winter growth among continental states.

Mask-growth rate correlation was only evident at minima. This may be an artifact of faster growth at fewer normalized cases, as well as regional differences in case prevalence early in the pandemic. States in the high mask quintile grew at similar rates as states in the low mask quintile after maxima (when interstate total case differences were smaller than before minima).

In addition, mask use did not predict normalized cases at minima, and low mask growth curves trailed those of high mask (particularly Northeast) states before minima. Growth maxima and Fall-Winter surges did not differ between Northeast and other states. Northeast states exhibited the highest seroprevalence up to at least July 2020 [24] and constituted 80% of the top quintile of mask use, which may explain their comparatively lower Summer growth.

Overall, mask use appears to be an intra-state lagging indicator of case growth. There is inferential but not demonstrable evidence that masks reduce SARS-CoV-2 transmission. Animal models [25], small case studies [6], and growth curves for mandate-only states [16] suggest that mask efficacy increases with mask use [11]. However, we did not observe lower growth rates over a range of compliance at maximum Fall-Winter growth (45-83% between South Dakota and Massachusetts during maxima) [17] when growth rates were high.

This complements a Danish RCT from 3 April to 2 June 2020, when growth rates were low, which found no association between mask use and lower COVID-19 rates either for all participants in the masked arm (47% strong compliance) or for strongly compliant participants only [8].

Masks have generally not protected against other respiratory viruses. Higher self-reported mask use protected against SARS-CoV-1 in Beijing residents [26], but RCTs found no differences in PCR confirmed influenza among Hong Kong households assigned to hand hygiene with or without masks (mask use 31% and 49%, respectively) [27].

Medical and cloth masks did not reduce viral respiratory infections among clinicians in Vietnam [9] or China [10], and rhinovirus transmission increased among universally masked Hong Kong students and teachers in 2020 compared with prior years [28].

These findings are consistent with a 2020 CDC meta-analysis [29] and a 2020 Cochrane review update [30].

Our study has implications for respiratory virus mitigation. Public health measures should ethically promote behaviors that prevent communicable diseases. The sudden onset of COVID-19 compelled adoption of mask mandates before efficacy could be evaluated.

Our findings do not support the hypothesis that SARS-CoV-2 transmission rates decrease with greater public mask use.

As masks are required in public in many US states, it is prudent to weigh potential benefits with harms. Masks may promote social cohesion as rallying symbols during a pandemic [31], but risk compensation can also occur [32]. Prolonged mask use (>4 hours per day) promotes facial alkalinization and inadvertently encourages dehydration, which in turn can enhance barrier breakdown and bacterial infection risk [33].

British clinicians have reported masks to increase headaches and sweating and decrease cognitive precision [34]. Survey bias notwithstanding, these sequelae are associated with medical errors [35]. By obscuring nonverbal communication, masks interfere with social learning in children [36]. Likewise, masks can distort verbal speech and remove visual cues to the detriment of individuals with hearing loss; clear face-shields improve visual integration, but there is a corresponding loss of sound quality [37, 38].

Future research is necessary to better understand the risks of long-term daily mask use [30]. Conversely, it 12 is appropriate to emphasize interventions with demonstrated or probable efficacy against COVID-19 such as vaccination [39] and Vitamin D repletion [40]. In summary, mask mandates and use were poor predictors of COVID-19 spread in US states. Case growth was independent of mandates at low and high rates of community spread, and mask use did not predict case growth during the Summer or Fall-Winter waves.

Strengths of our study include using two mask metrics to evaluate association with COVID-19 growth rates; measuring normalized case growth in mandate and non-mandate states at comparable times to quantify the likely effect of mandates; and deconvolving the effect of mask use by examining case growth in states with variable mask use. Our study also has key limitations. We did not assess counties or localities, which may trend independently of state averages.

While dense sampling promotes convergence, IHME masking estimates are subject to survey bias. We only assessed one biological quantity (confirmed and probable COVID-19 infections), but the ongoing pandemic warrants assessment of other factors such as hospitalizations and mortality. Future work is necessary to elucidate better predictors of COVID-19 spread. A recent study found that at typical respiratory fluence rates, medical masks decrease airway deposition of 10-20μm SARS-CoV-2 particles but not 1-5μm SARS-CoV-2 aerosols [41].

Aerosol expulsion increases with COVID-19 disease severity in non-human primates, as well as with age and BMI in humans without COVID-19 [42]. Aerosol treatment by enhanced ventilation and air purification could help reduce the size of COVID-19 outbreaks.

See more here: medrxiv.org

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