Important Study on Masking & Evidence: Does CDC Use Junk Science to Promulgate Mask Mandates?

By Staff at TrialSite

A trio of well-respected University of California, San Francisco (UCSF)-affiliated medical researchers recently conducted a retrospective cross-sectional study of regular weekly reports generated by the Centers for Disease Control and Prevention (CDC) known as the MMWR publication with a focus on the subject of masks covering the time period of 1978 to 2023. This study’s main question concerns mask effectiveness. The importance of this investigation uploaded to the preprint server medRxiv should not be understated—the MMWR reports have substantial influence on American public health policy, if not beyond. While not peer reviewed, TrialSite has suggested in multiple analyses how MMWR output was exploited during the pandemic by political forces to effectuate various policies and agendas. Hence, the importance of a critical vetting of the scientific process associated with the CDCs output. The topic of concern with this latest piece concerns mask policies during COVID-19. Ultimately, 77 studies published since 2019 met the authors’ study design inclusion criteria, with 97.4% of these studies originating in the United States. Not surprisingly, observational studies without a comparator group 22/77 (28.6%) were most frequent. As was the case often with COVID-19 vaccine analysis in MMWR, community settings in this systematic analysis were most common (36/77; 45.5%). Not one randomized study was identified even though this category of study generates the strongest evidence. Of the analysis, 23/77 (29.9%) assessed mask effectiveness, with 11/77 (14.3%) being statistically significant, yet the great majority 58/77 (75.3%) stating masks as effective. Out of those, 41/58 (70.7%) used causal language. The authors found that just one mannequin study actually employed use of causal language in the appropriate manner (1.3%). 72/77 (93.5%) of the studies related to SARS-CoV-2 only, and none of these studies cited randomized data. Just one study (1/77 (1.3%) cited conflicting evidence. The bombshell finding: “MMWR publications pertaining to masks drew positive conclusions about mask effectiveness over 75% of the time despite only 30% testing masks and <15% having statistically significant results. No studies were randomized, yet over half drew conclusions were most often unsupported by the data. Our findings raise concern about the reliability of the journal for informing health policy.”

The study makes important points that cannot be ignored, let alone discounted. While the results are not yet peer reviewed, and generally evidence needs that validation (and this is no exception), TrialSite has monitored the CDC’s use of the MMWR during the pandemic and repeatedly reported on what appeared to be successful attempts at influencing various societally important decisions without the necessary evidence. Put another way, these CDC reports appear to serve as a justification for various decisions and policies, less the sufficient evidence justifying any particular decision or policy.

For example, during November 2022, TrialSite introduced, “CDC Releases Limited Data Snapshot: White House Exploits for Sweeping Declarations of Bivalent Vaccine Booster Success.” This MMWR output was timed conveniently to coincide with a White House COVID-19 press briefing touting the success of the bivalent BA4/BA5 mRNA booster vaccines. The product had just been authorized two months previous, and uptake was slow. While the data in this MMWR had severe limitations which are explained in the TrialSite article, the White House used the data output for backing sweeping declarations of vaccine success.

The subject: masking

In this latest study, corresponding author Tracy Høeg, M.D., Ph.D. Department of Epidemiology and Biostatistics at University of California, San Francisco, (UCSF), and two colleagues, also from UCSF Alyson Haslam, Ph.D. and Vinay Prasad, M.D., MPH convey that before the COVID-19 pandemic, evidence was lacking for surgical and N95 respirator masks in the community and healthcare setting. In fact, prior to the pandemic, the CDC had never recommended mask wearing for health members of the population, which aligns with the general advisory of the Surgeon General.

Background

Yet, despite the lack of evidence Høeg and colleagues shared in the United States, “Over several weeks in March and early April 2020, a coordinated social media campaign to recommend masks began.” By April 3, 2020, the CDC then recommended that persons aged 2 years and up wear a cloth face covering in public. By July 15, then CDC director Rochelle Walensky issued the recommendation that all Americans don a mask as a means to “get the epidemic under control.” The evidence backing this claim: a MMWR study involving two hairstylists in Missouri. Universal masking ensued by the fall of 2020—in schools and day care facilities for example per CDC recommendations. Next came the widespread mandates enacted at the state, county and school district levels for children down to the age of two. By January 2021, federal mandates led to mandates for masking on public transport.

Conclusion

Despite the overwhelming influence of the MMWR during the COVID-19 as described above, less than 20% of these weekly reports targeting masks were based on any statistical evidence of mask effectiveness. The CDC used no randomized studies while 75% of their weekly tracking output led to a favorable conclusion about the use of masks and SARS-CoV-2. As TrialSite has explained with these same reports and the COVID-19 vaccines, MMWR data output are used by health authorities and governing agencies to support and back various policy measures.

This, despite the fact that there was a complete lack of any evidence for mask effectiveness according to the authors’ study. In this important study, the trio of well-respected San Francisco-based authors point out the need for caution and output from the MMWR. Their findings lead them to observe “the journal’s lack of reliance on high-quality data and a tendency to make strong but unsupported causal conclusions about mask effectiveness.” The systematic embrace and use of subpar scientific evidence to back profound societal policies, emergency or not, must be critically vetted.