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Occupational risk of COVID-19 in the 1st vs 2nd wave of infection

Our take —

This study, available as a preprint and thus not yet peer reviewed, found that there was a shift in the burden of COVID-19 cases between the first (February-mid-July 2020) and second wave (mid-July-October 2020) of the pandemic based on electronic medical record data from all individuals aged 20-70 years old in Norway. During the first wave, healthcare professionals had the highest odds of infection, however individuals working in the food service industry (bartenders, waiters, etc.) and travel stewards were disproportionately affected during the second wave. Transportation workers had higher odds of infection compared to others of working age during both waves. These data provide comprehensive descriptive information about the shifting demographics of the pandemic and can be used to inform current and future responses to the pandemic.

Study design

Cross-Sectional

Study population and setting

Using data from an emergency preparedness register (BEREDT C19 register) that captured electronic patient records, surveillance data, and employment data for all Norwegian residents (both native and immigrants), this study examined differences in COVID-19 diagnoses and hospitalizations by profession. COVID-19 diagnosis was defined as a positive PCR test or a positive ICD-10 diagnostic code of COVID-19 (U07.1). To be included in the study, individuals had to be between 20 and 70 years old on January 1, 2020, and have a unique personal identification number. Tourists, temporary workers, and asylum seekers were excluded. Occupation was recorded based on the Norwegian Standard Classification of Occupation (STYRK-98) and was aligned to international designations based on the Standard Classification of Occupations. The focus of this study was on occupations having direct contact with others, e.g. health, teaching, sales, cleaners, food service, travel and transportation, recreation and beauty. The first wave of COVID-19 infection was defined as being from February 26 to July 17, 2020, and the second wave from July 18 to October 20, 2020. Crude and adjusted multivariable logistic regression were used to assess the association between occupation and: 1) COVID-19 diagnosis, and 2) hospitalization. Age, sex, and country of birth were adjusted for in the adjusted model.

Summary of Main Findings

A total of 3.5 million individuals were included in this study, of which 0.3% were diagnosed with COVID-19 (n=12,736). During the 1st wave, health care professionals (nurses, physicians, dentists) and transportation works (bus/tram and taxi drivers) had a significantly greater odds of infection (1.5-3.5 times the odds of infection) when compared to everyone else of working age. During the 2nd wave, food service industry workers and transportation workers, again, were disproportionately affected (bartenders, waiters, taxi drivers, travel stewards) with 1.5-4 times the odds of infection. In both waves, there was limited association between occupation type and odds of hospitalization.

Study Strengths

The use of a national emergency preparedness register, linked to employment records, allows for the examination of the entire working age population of Norway for the duration of the pandemic.

Limitations

There is limited information provided on how testing guidelines and protocols evolved over time, which would be of particular importance here given that the study aims to compare those who tested positive during two different time periods. Overall, 24.4% of the sample could not be categorized using the available registry data (e.g. unemployed or not registered with any occupation). There is the possibility that the distribution of occupational status may be different among unregistered individuals which may influence the interpretation of findings. Additionally, the low number of hospitalizations in some professions created very wide confidence intervals, and the limited association between occupation and severe COVID-19 (hospitalization) should be interpreted with caution.

Value added

This study provides valuable descriptive data on occupational groups most impacted by COVID-19 over the course of the pandemic.

This review was posted on: 3 January 2021