Ivy League researchers conducted a massive randomized control trial of community cloth and surgical mask use in Bangladesh. Pundits claim this study "confirms" that community cloth and surgical mask use reduces COVID-19 transmission rates. Pundits are grossly exaggerating.
Beaming are the reports about the new large-scale randomized control trial mask study conducted by Ivy League researchers in Bangladesh. The trial involving a sample size of 342,126 participants was, indeed, monumental, and was conducted across hundreds of rural villages in Bangladesh from November 2020 through March 2021. Academy and news media are enthusiastically reporting that the new research “confirms” that cloth and surgical masks reduce COVID-19 transmission by up to 11.2%. Undoubtedly this study was so important that the researchers couldn’t wait to publish in a medical journal, so, on August 31, 2021, they self-published the Bangladesh findings on the Innovations for Poverty Action website.
Perhaps you’d be surprised then to learn that to construe this study’s findings as “confirm[ing]” an 11.2% reduction in COVID-19 transmission requires number fudging and exaggeration not present in previous RCT mask studies. In reality, the purported reduction in COVID-19 transmission achieved by cloth and surgical masks as demonstrated by this study is merely 0.07%. That’s right, we’re talking about a minuscule, 7 hundredths of 1 percent purported reduction in transmission that, in any other era not dominated by hyper-partisan totalitarian politics, should be statistically meaningless.
At the outset I can't resist highlighting the silent part that the “science” community is now proclaiming out loud while showering adulation upon the Bangladesh mask study. Indeed, it is now popular to openly acknowledge that randomized control trial studies (“RCTs”) are the "gold standard" for conducting cause and effect research that, for example, evaluates whether interventions like masks reduce community transmission of viral infections. However, similar to nearly all previous RCT mask studies conducted using much smaller sample sizes, the Bangladesh study — once sufficiently filtered of its politically viral smoke screen (see what I did there?) — once again demonstrates that cloth and surgical masks provide, at best, practically zero benefit in reducing community spread of airborne viruses like SARS-CoV-2.
The renewed mainstream acknowledgment that RCTs are the best method for evaluating the real world impact of interventions in community settings bespeaks the CDC’s own brittle cloth and surgical mask guidance. While the CDC relied upon 65 mask studies as the basis for its guidance, only two of those studies were RCTs. Furthermore, both RCTs that the CDC referenced prove the effective futility of cloth and surgical masks at mitigating community transmission of viral illnesses. Naturally the CDC singled out those two studies in its mask guidance paper for criticism as they purportedly did not test across sufficiently large sample sizes. I have described the gaping holes in the CDC’s mask guidance at length in my last article.
In any case, let’s take a closer look at the Bangladesh study so that we can understand what it actually demonstrates. The Bangladesh mask study’s multi-pronged purpose encompassed 1) determining whether cloth and surgical masks reduce community COVID-19 transmission, and 2) evaluating various methods of community mask promotion to determine the best method for increasing community mask use. I’m not going to discuss the 2nd prong of the study at length other than to mention that researchers determined that employing in-person mask evangelists (effectively street preachers in public places extolling the virtues of mask wearing) — as opposed to attempting to motivate communities through financial incentives and altruistic virtue signaling — was the best way to increase community masking across the Bangladesh study population.
The researchers employed observers in 600 mostly rural villages across Bangladesh during staggered 8-week intervention periods to record mask wearing patterns. The first observation periods began in November 2020, and the last observation periods began in January 2021. The 600 villages were divided into 300 control villages (no mask promotion) and 300 mask intervention villages (where either cloth or surgical masks were freely distributed AND promoted). It’s also worth mentioning that observation periods from November 2020 to March 2021 in Bangladesh occurred during a downward trend of exclusively alpha variant COVID-19 transmission. As such, the meager 0.07% reduction in COVID-19 transmission purportedly attributed to masking would likely not translate to the far more transmissible Delta variant.
Out of all the 342,126 participants across 300 mask intervention villages and 300 control villages, 335,382 (98%) responded to the researchers’ survey asking whether the participants experienced COVID-19-like symptoms during the staggered 8-week study periods. A total of 27,166 participants (8.1% of the respondents) reported experiencing these symptoms. Of the 8.1% of respondents reporting COVID-19-like symptoms, only 40.3%, or 10,952, agreed to have their blood collected and tested for the seroprevalence of SARS-CoV-2 IgG antibodies. 39.9% of the 10,952 blood test volunteers came from the control group and 40.8% came from the mask intervention group. There was a significant portion of remaining samples that could not be tested for various reasons. Interestingly the researchers explicitly stated that the 0.9 percentage point difference in the number of blood test volunteers from the intervention and control groups was not statistically significant.
"Of these, 10,952 (40.3%) consented to have blood collected, including 40.8% in the treatment group and 39.9% in the control group (the difference in consent rates is not statistically significant, p = 0.24)."
I can’t overstate the last sentence of the previous paragraph enough — the researchers explicitly stated that 0.9 percentage point difference between the number of blood test volunteers from the mask groups and control group was not statistically significant. It is therefore baffling that these same researchers a few pages down in their report concluded that a difference between the 0.76% of the control group that tested positive for COVID-19 versus the 0.69% of the mask group that tested positive is of any statistical significance. For the math-impaired, that is a 0.07 percentage point reduction in the number of mask group samples testing positive for COVID-19 versus the number of control group samples testing positive. For context, this 0.07 percentage point difference is nearly 13 times smaller than the 0.9 percentage point difference between the number of the blood test volunteers from the control group and mask group that these same researchers explicitly claimed to be statistically insignificant. The internal inconsistency would be staggering but for the clear political and authoritarian motivations dominating the COVID-19 mitigation debate.
The researchers further broke out the positive test results between cloth and surgical mask groups to reveal that, while 0.76% of the control group tested positive for COVID-19 antibodies, 0.74% of the cloth mask group and 0.67% of the surgical mask group tested positive, respectively. In other words, there was only a 0.02 percentage point reduction in infection rate when comparing the cloth mask group to the control group and only a 0.09 percentage point reduction in infection rate when performing the same comparison with the surgical mask group
To exaggerate these infinitesimal reductions in purported COVID-19 infection rates between the mask groups and the control group, the researchers employed some trickery. Rather than simply concluding that 0.02 and 0.09 percentage point purported reductions in COVID-19 infections were not statistically significant just as they described a much higher 0.9 percentage point difference between the number of control group and mask intervention group test samples earlier in their report, the researchers derived an 11.2% infection reduction value by computing the hundredths of 1% differences between the control group and mask group infection rates as relative reductions. In other words, researchers set the 0.76% COVID-19 positive rate among the control group as the baseline reference point to which the percentage point differences of .02 and .09 in the cloth and surgical mask groups were calculated as percentages of 0.76% rather than differences. By doing this, the researchers and their sycophantic media mouthpieces can claim that, for example, surgical masks reduce COVID-19 transmission by 11.2% as 0.09 percentage points are approximately 11.2% of 0.76%.
Accordingly, unlike previous RCT mask studies published in medical journals, such as the 2020 Danish study where researchers explicitly concluded that the 0.3 percentage point reduction in COVID-19 infection rate found in the mask group compared to the control group was not statistically significant and, in fact, suggested a range of outcomes that included the possibility that masks increase COVID-19 transmission, the Bangladesh researchers brush aside the infinitesimally small 0.07 percentage point difference in infection rates between the control and mask groups by neglecting to mention that this difference is not statistically significant. By engaging in this cynical form of number fudging, proponents of the Bangladesh study can triumphantly report that surgical masks reduce COVID-19 transmission by 11.2%. While the Bangladesh report itself is honest enough to refer to the purported 11.2% reduction as a relative reduction, nearly all reporting from establishment media outlets surrounding this study fail to explain or even acknowledge this distinction.
Again, the infinitesimally small difference between the infection rates in the control group and mask groups indicated by the Bangladesh RCT continues to signal that cloth and surgical masks do practically nothing to prevent community transmission of SARS-CoV-2. Other weak links in the Bangladesh study include the fact that observers witnessed a 5% increase in social distancing within the mask intervention group compared to the control group. This is a confounding factor independent of mask wearing that, alone, could account for the meager 0.09 percentage point reduction in COVID-19 infection observed in the surgical mask intervention group compared to the control group. Likewise, it seems strange that the researchers would limit blood testing to only those survey respondents who reported experiencing COVID-19-like symptoms when it is widely held that nearly half of all infected by the pandemic virus never experience symptom. More testing across a wider asymptomatic subpopulation of the Bangladesh study’s abundant number of participants would have likely been beneficial.
Ultimately, the stated degree that community cloth and surgical masking functions to reduce COVID-19 transmission according to the messaging surrounding the Bangladesh study is vastly overstated. As the researchers tacitly acknowledged by their own internally inconsistent reporting, the 0.02 to 0.09 percentage point reduction in transmission rates purportedly observed in mask control groups are not statistically significant. Therefore, despite all the hubbub to the contrary, the Bangladesh study should be soberly understood as yet another “gold standard” RCT demonstrating the futility of community cloth and surgical mask use in mitigating SARS-CoV-2 transmission.