Effectiveness of Face Mask or Respirator Use in Indoor Public Settings for Prevention of SARS-CoV-2 Infection — California, February–December 2021

Andrejko, Kristin L; Pry, Jake; Myers, Jennifer F.; Fukui, Nozomi; DeGuzman, Jennifer L.; Openshaw, John J.; Watt, James; Lewnard, Joseph A; Jain, Seema; Abdulrahim, Yasmine; Barbaduomo, Camilla M.; Bermejo, Miriam I; Cheunkarndee, Julia; Cornejo, Adrian F.; Corredor, Savannah; Dabbagh, Najla; Dong, Zihui; Dyke, Ashly; Fang, Anna T.; Felipe, Diana; Frost, Paulina M.; Ho, Tammy Szu-Yu; Javadi, Mahsa; Kaur, Amandeep; Lam, Amanda Yun Rui; Li, Sophia S.; Miller, Monique; Ni, Jessica; Park, Hyemin; Poindexter, Diana J.; Samani, Helia; Saretha, Shrey; Spencer, Maya; Spinosa, Michelle M.; Tran, Vivian; Walas, Nikolina; Wan, Christine; Xavier, Erin

doi:10.15585/mmwr.mm7106e1

Cited by 167 publications

(153 citation statements)

References 7 publications

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“…Therefore, lower prevalence of positive test results over time and after asymptomatic infections might reflect lower infectiousness. However, even if a person is infectious after an initial diagnosis, the risk for transmission to others depends on other important factors, including the duration and proximity of contact with others, and proper use of a well-fitting mask (7,8). Following CDC recommendations, § § YKHC advised continued mask use for 10 days after symptom onset even if a person met the criteria for ending isolation after 5 days.…”

Section: Discussionmentioning

confidence: 99%

Antigen Test Positivity After COVID-19 Isolation — Yukon-Kuskokwim Delta Region, Alaska, January–February 2022

Lefferts¹,

Blake²,

Bruden³

et al. 2022

MMWR Morb. Mortal. Wkly. Rep.

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Section: Discussionmentioning

confidence: 99%

Antigen Test Positivity After COVID-19 Isolation — Yukon-Kuskokwim Delta Region, Alaska, January–February 2022

Lefferts¹,

Blake²,

Bruden³

et al. 2022

MMWR Morb. Mortal. Wkly. Rep.

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“…24 Finally, protections in workplace settings remain crucial. Given that SARS-CoV-2 can be transmitted via aerosols, 25,26 we urge for free provision of masks-preferably N95 masks or similarly effective masks 27,28 -to essential workers and improved ventilation in workplace settings. 29 We acknowledge challenges related to measurement of occupation on death certificates, and questions relating to whether risks are necessarily related to workplace exposures.…”

Section: Discussionmentioning

confidence: 99%

“…24 Finally, protections in workplace settings remain crucial. Given that SARS-CoV-2 can be transmitted via aerosols, 25,26 we urge for free provision of masks—preferably N95 masks or similarly effective masks 27,28 —to essential workers and improved ventilation in workplace settings. 29…”

Section: Discussionmentioning

confidence: 99%

COVID-19 mortality and excess mortality among working-age Californians, by occupational sector: March 2020 through November 2021

Chen

Riley

Duchowny

et al. 2022

Preprint

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BackgroundDuring the first year of the pandemic, essential workers faced higher rates of SARS-CoV-2 infection and COVID-19 mortality than non-essential workers. It is unknown whether disparities in pandemic-related mortality across occupational sectors have continued to occur, amidst SARS-CoV-2 variants and vaccine availability.MethodsWe obtained data on all deaths occurring in the state of California from 2016 through 2021. We restricted our analysis to California residents who were working age (18–65 years at time of death) and died of natural causes. Occupational sector was classified into 9 essential sectors; non-essential; or not in the labor market. We calculated the number of COVID-19 deaths in total and per capita that occurred in each occupational sector. Separately, using autoregressive integrated moving average models, we estimated total, per-capita, and relative excess natural-cause mortality by week between March 1, 2020, and November 30, 2021, stratifying by occupational sector. We additionally stratified analyses of occupational risk into regions with high versus low vaccine uptake, categorizing high-uptake regions as counties where at least 50% of the population completed a vaccination series by August 1, 2021.FindingsFrom March 2020 through November 2021, essential work was associated with higher COVID-19 and excess mortality compared with non-essential work, with the highest per-capita COVID-19 mortality in agriculture (131.8 per 100,000), transportation/logistics (107.1), manufacturing (103.3), and facilities (101.1). Essential workers continued to face higher COVID-19 and excess mortality during the period of widely available vaccines (March through November 2021). Between July and November 2021, emergency workers experienced higher per-capita COVID-19 mortality (113.7) than workers from any other sector. Essential workers faced the highest COVID-19 mortality in counties with low vaccination rates, a difference that was more pronounced during the period of the Delta surge in Summer 2021.InterpretationEssential workers have continued to bear the brunt of high COVID-19 and excess mortality throughout the pandemic, particularly in the agriculture, emergency, manufacturing, facilities, and transportation/logistics sectors. This high death toll has continued during periods of vaccine availability and the delta surge. In an ongoing pandemic without widespread vaccine coverage and anticipated threats of new variants, the US must actively adopt policies to more adequately protect essential workers.

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“…For the FFP2 masks, the overall considered reduction effect has been assumed to be 80% (Poydenot et al, 2021). In a Californian study using case data between February to December 2021 (Andrejko et al, 2022), using a face mask or respirator in indoor public settings was associated with lower odds of acquiring SARS-CoV-2 infection, with protection being highest among those who reported wearing an N95/KN95 respirator, followed by wearing a surgical mask, and a cloth mask.…”

Section: Assessment Of Impact Of Administrative Controls and Vaccinationmentioning

confidence: 99%

A tracer gas study of ventilation and air movement to inform potential SARS-CoV-2 airborne transmission

Linge

Palmer

Downey

et al. 2022

Preprint

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Tracer gas studies were carried out to investigate the potential for airborne transmission of SARS-CoV-2 variants, and to inform work practises to reduce COVID-19 exposure and transmission. The air exchange of a meeting room was determined in accordance with ASTM E741-11 using sulfur hexafluoride (SF6), a colourless, odorless, non-flammable, and non-toxic tracer gas. Air was generally well mixed in the room, and very little tracer gas escaped through the closed door. The calculated air changes per hour (ACH) of the meeting room (5.8 h-1) was higher than the value recommended for offices (2-3 h-1) and used to assess potential COVID-19 infection risk and calculate maximum occupancy rates using the Airborne Infection Risk Calculator (AIRC) V3 Beta. Results showed that the previous guidance for maximum occupancy rates provided by many Australian States and Territories (the 2 or 4 square meters rule) provides a conservative estimate of the maximum number of occupants within a room for exposure events of up to 2 hours. However, for longer periods, such as a full working day (7.5 hours), and for more infectious strains of SARS-CoV-2, the 2 or 4 square meter rule did not adequately address infection risk. Use of two additional controls, mask wearing and ensuring that all occupants had received a third boosted vaccine dose, was estimated to reduce the probability of infection by 3.75-fold assuming infection with the Omicron variant. Including both controls increased the predicted maximum occupancy to values greater than the 2 and 4 square meter rule for most scenarios. Air movement outside the meeting room was investigated by filling the room with tracer gas and allowing the air to move freely by keeping the door open. Airflow was most influenced by the ventilation system of the laboratories in the north wing of building, rather than laboratories in the south wing. The plug of tracer gas was largely removed from the building within 30 minutes, although detectable concentrations were measured in some areas with lower air flow at the end of the 2-hour experiment. High concentrations were also noted in front of the elevators, however tracer gas concentrations were below detection on other floors. The techniques employed in this study are suitable for measuring air movement and ventilation in other buildings where aerosol transmission of COVID-19 is of concern.

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Effectiveness of Face Mask or Respirator Use in Indoor Public Settings for Prevention of SARS-CoV-2 Infection — California, February–December 2021

Cited by 167 publications

References 7 publications

Antigen Test Positivity After COVID-19 Isolation — Yukon-Kuskokwim Delta Region, Alaska, January–February 2022

Antigen Test Positivity After COVID-19 Isolation — Yukon-Kuskokwim Delta Region, Alaska, January–February 2022

COVID-19 mortality and excess mortality among working-age Californians, by occupational sector: March 2020 through November 2021

A tracer gas study of ventilation and air movement to inform potential SARS-CoV-2 airborne transmission

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