Scientists and healthcare officials have developed several pharmaceutical and non-pharmaceutical interventions to contain the ongoing coronavirus disease 2019 (COVID-19) pandemic. For example, wearing facemasks has been one of the most effective non-pharmaceutical measures that have been adopted globally to prevent the further spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and protect individuals from contracting COVID-19.
Study: Maintaining face mask use before and after achieving different COVID-19 vaccination coverage levels: a modelling study. Image Credit: Mr. Tempter / Shutterstock.com
Background
Early on in the COVID-19 pandemic, most people wore facemasks in the United States. However, researchers observed that this practice relaxed since the spring of 2021, even though the vaccination rates were below that which has been projected to attain herd-immunity thresholds.
In mid-May 2021, the U.S. Centers for Disease Control and Prevention (CDC) announced that vaccinated individuals were not required to wear facemasks when they were indoors in public places like restaurants. This prompted both vaccinated and unvaccinated individuals to stop wearing facemasks, which was quickly followed by a significant rise in COVID-19 cases due to the SARS-CoV-2 Delta (B.1.617.2) and Omicron (B.1.1.529) variants.
This surge in COVID-19 cases quickly caused local officials to reinstate facemask requirements in Los Angeles County, California, and Washington D.C. Although various studies have shown that facemasks effectively prevent SARS-CoV-2 transmission, the use of facemasks in 2021 remained lower than it was in 2020.
About the study
Recently, researchers have addressed some important questions regarding the use of facemasks, such as whether facemasks should be worn in public indoor locations like grocery stores and public transportation, and for how long this practice should be maintained.
In this context, scientists in a recent The Lancet Public Health study simulated different scenarios using facemasks through a computational Monte Carlo simulation model representing the population of the U.S. and SARS-CoV-2 transmission. Moreover, the researchers performed simulations to compare different scenarios, which included predictions of the outcomes for individuals who wore a facemask and those who did not use a facemask until the target vaccination coverage of 70-90% of the population was achieved.
Study findings
The current study underscored that COVID-19 vaccination alone is not enough to manage the pandemic. Multiple interventions were required to prevent transmission of SARS-CoV-2, death, and suffering.
As each intervention including the frequent use of sanitizers, face masks, and social restrictions is associated with different limitations, a combinational effect of multiple interventions could positively enhance their impact and combat the pandemic.
The authors provided strong evidence that showed the use of facemasks is an effective and cost-effective method to manage the COVID-19 pandemic. The current study also revealed that facemasks must be used continuously, even after reaching specific vaccination coverage levels to attain herd immunity.
Continual use of facemasks is important, as virus transmission does not immediately cease on reaching vaccination threshold levels. In fact, facemasks appear to provide additional prevention until transmission gradually recedes after two to ten weeks.
The decline of vaccine effectiveness as a result of the emergence of new SARS-CoV-2 variants and waning of immune responses induced by vaccination or natural infection have increased the value of wearing facemasks.
The researchers note that it is not realistic to presume that all individuals with COVID-19 would remain isolated for the full duration of their infected phase. This is because many people do not get tested for SARS-CoV-2 infection, asymptomatically infected individuals might transmit infection unintentionally, or some patients might be tempted not to remain isolated throughout the infected phase. This situation further emphasizes the importance of using facemasks to control the pandemic.
The authors recommend that all individuals continue to wear facemasks, irrespective of their age group or profession. When face mask effectiveness was increased by 10%, a relative reduction of 17–20% of COVID-19 cases was observed. Additionally, a significant reduction in the number of hospitalizations and deaths due to SARS-CoV-2 infection was reported.
Study takeaways
Although the current model is based in the U.S., these findings can resemble similar scenarios in other countries. Furthermore, all models represent a simplified version of real-life conditions and cannot account for every possible outcome.
In the event that there is a shortage of effective facemasks, such as N95 masks, wearing a regular cloth mask is better than not wearing one, as individuals with COVID-19 are less likely to spread the disease when they use facemasks. Taken together, the researchers suggest the continual wearing of facemasks for two to ten weeks beyond achieving specific vaccination coverages to reduce residual SAR-CoV-2 transmission.
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