Effects of universal masking on Massachusetts healthcare workers’ COVID-19 incidence

• Published in: Occupational medicine (Oxford) Vol. 70; no. 8; pp. 606 - 609
• Main Authors: Lan, F-Y, Christophi, C A, Buley, J, Iliaki, E, Bruno-Murtha, L A, Sayah, A J, Kales, S N
• Format: Journal Article
• Language: English
• Published: UK Oxford University Press 12.12.2020
• Subjects: Adult; COVID-19 - epidemiology; COVID-19 - prevention & control; COVID-19 - virology; Female; Health Personnel - statistics & numerical data; Humans; Incidence; Infection Control - statistics & numerical data; Male; Masks - statistics & numerical data; Massachusetts - epidemiology; Middle Aged; Occupational Diseases - epidemiology; Occupational Diseases - prevention & control; Occupational Diseases - virology; SARS-CoV-2; Short Report; Massachusetts; SARS-CoV-2; infection control; personal protective equipment; Hospital; infectious disease
• ISSN: 0962-7480; 1471-8405
• DOI: 10.1093/occmed/kqaa179

Abstract Background Healthcare workers (HCWs) and other essential workers are at risk of occupational infection during the COVID-19 pandemic. Several infection control strategies have been implemented. Evidence shows that universal masking can mitigate COVID-19 infection, though existing research is limited by secular trend bias. Aims To investigate the effect of hospital universal masking on COVID-19 incidence among HCWs compared to the general population. Methods We compared the 7-day average incidence rates between a Massachusetts (USA) healthcare system and Massachusetts residents statewide. The study period was from 17 March (the date of first incident case in the healthcare system) to 6 May (the date Massachusetts implemented public masking). The healthcare system implemented universal masking on 26 March, we allotted a 5-day lag for effect onset and peak COVID-19 incidence in Massachusetts was 20 April. Thus, we categorized 17–31 March as the pre-intervention phase, 1–20 April the intervention phase and 21 April to 6 May the epidemic decline phase. Temporal incidence trends (i.e. 7-day average slopes) were compared using standardized coefficients from linear regression models. Results The standardized coefficients were similar between the healthcare system and the state in both the pre-intervention and epidemic decline phases. During the intervention phase, the healthcare system’s epidemic slope became negative (standardized β: −0.68, 95% CI: −1.06 to −0.31), while Massachusetts’ slope remained positive (standardized β: 0.99, 95% CI: 0.94 to 1.05). Conclusions Universal masking was associated with a decreasing COVID-19 incidence trend among HCWs, while the infection rate continued to rise in the surrounding community.