Global Assessment of the Impact of Masking on COVID-19: A Country Level Comparative and Retrospective Analyses Using the Richards Model
Background: Within four months since the first reported case in Wuhan, China, corona virus disease 2019 (COVID-19) spread to more than 200 countries. Since the initially reported cases in each country until mid-August 2020, country-specific interventions on masking were decentralized. Many types of masks are effective under laboratory conditions. But people wear mask inconsistently and imperfectly in the real-world. The extent by which the effectiveness of masking when mandated at a country level for multiple countries/regions reduces severe acute respiratory syndrome 2 (SARS-CoV-2) transmission has not been analyzed. Additionally, the question exists if the type of mask worn, i.e., cloth mask, surgical mask, and bandana, were effective in halting the transmission of SARS-CoV-2. Therefore, using the Richards model, a phenomenological method, we investigated differences in the infection rate (r), turning point (ti), and curve steepness (α) of the COVID-19 outbreak among 177 countries to assess the impact of masking policy and the type of mask in containing the COVID-19.
Methods: We used the daily cumulative infection cases from the first reported case until August 19, 2020 for 177 countries/region taken from www.ourworldindata.org , a publicly available COVID-19 data repository. Using data for each country, we derived the r, ti, and α of COVID-19 by fitting them to the Richards model. Data fitting was performed manually in IgorPro software. We evaluated goodness of fit by minimizing the χ2 .
Findings: Our analysis revealed that global COVID-19 estimates of α = 0.009 – 4.3 (95% confidence interval (CI95%), 0.005 – 0.680), r = 0.008 – 0.50 (CI95%: 0.0001 – 0.0045), and ti = 0.58 – 315.92 (CI95%: 0.02 – 36.85). The estimated range was within the limit for both countries with and without mask mandates for single and multiple wave cases. Additionally, an early masking mandate did not correlate with a shorter ti.
Interpretation: Based on the phenomenological Richards model, this retrospective study’s findings indicate no significant difference in r, ti, and α between countries with and without mask mandate. Therefore, many laboratory and modeling studies on masking did not translate to a measurable difference in the real world for many countries based on our fitting. Effectiveness of masking coupled with other non-pharmaceutical interventions depends on the measures carried out by a specific country/region. This result implies that mask enforcement policy and the type of mask use (e.g., surgical, cloth) could not have significantly reduced SARS-CoV-2 transmission. Therefore, more stringent protection such as N95 combined with other control measures such as enhanced indoor ventilation, a longer social distancing recommendation may be necessary to disrupt SARS-CoV-2 transmission effectively. Therefore, selecting the mask type is critical to effectively disrupt the transmission of SARS-COV-2, which is primarily transmitted via aerosols.
Digital Object Identifier (DOI)
Preprint version SSRN Electronic Journal, 2021.
Mamun, M. M., & Vejerano, E. P. (2021). Global assessment of the impact of masking on COVID-19: A country level comparative and retrospective analyses using the Richards model. SSRN Electronic Journal. https://doi.org/10.2139/ssrn.3955742