Study explores which occupations had the greatest risk of SARS-CoV-2 infection and how relative differences varied over the pandemic

In a recent study posted to the medRxiv* preprint server, researchers investigated occupations at the highest risk for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection.

Background

It has been observed that some occupational groups have a higher COVID-19 infection and mortality rate. It is essential to protect workers from SARS-CoV-2 infection. Currently, it is being debated how viral transmission occurs in workplaces or which occupations are the most affected amid calls to classify long COVID as an occupational disease.

Thus, it is imperative to understand workplace risk to better inform COVID-19 policy and practice. Different studies have reported a higher risk of infection for healthcare and transport workers than non-essential workers. In contrast, some others have observed that risk varies by worker class or the stage of the COVID-19 pandemic.

About the study

In the present study, researchers analyzed data from the Office of National Statistics (ONS) COVID-19 infection survey (CIS) to determine the association between occupation and COVID-19 and identify works with the highest infection risk.

Moreover, the authors explored the variations in relative differences at different time points during COVID-19. The CIS data from April 2020 to November 2021 were analyzed and included all individuals aged 20 – 60 years. The association between occupation and infected individuals was confirmed with a polymerase chain reaction (PCR) test was examined using basic frequency tables. Only confirmed test results were studied and not self-reported results.

Time-varying Cox regression was used to analyze data to produce hazard ratios (HRs) at 95% confidence intervals (CIs). Data were divided into four-time points for studying the variations in relative differences over time and analyzed using a multi-level logistic regression model. The authors examined previous works and derived a plausible directed-acyclic graph (DAG) to base their adjustment set (SX).

The effects of socioeconomic status, health, or living conditions were not represented in the DAG. The SX variables were considered confounders instead of mediators, given the interest in defining/identifying short-term occupational effects. Adjustments for multiple individuals from the same residence were not made, nor were weights applied. The occupational effects across different models were compared using coefficient plots.

Findings

Over 312,300 working-age individuals participated in the CIS by November 2021, with about 8% having one PCR-confirmed COVID-19 test result. The mean age was 45 years, and females (55%) outnumbered males. Participants provided information on more than 3.9 million visits, with 12.5 mean visits per person.

More than 91% identified as ethnically White, and around 49% were working during the CIS and had information as four-digit standard occupational classification (SOC) 2010 codes. Increased infection risk was observed for social care staff, education sector employees, bus or coach drivers, and police and protective services compared to non-essential workers. An increase in infection risk was not apparent for healthcare support staff, food production, food retail and distribution, taxi/cab drivers, chauffeurs, van drivers, and other transport drivers.

Healthcare associate professionals had little evidence of any higher risk of infection. When multiple demographic factors were adjusted, marginal changes in HRs and CIs were observed. The healthcare workers, on average, had an increased risk of infection at different time points in the early COVID-19 pandemic.

For instance, elevated infection risk was noted during April 2020 – September 2020 (T1), October 2020 – February 2021 (T2), which diminished during March 2021 – May 2021 (T3), and June 2021 – October 2021 (T4). The combined group risk for social care and education workers did not increase during T1 but increased in T2 that persisted through T4. Higher infection risks, on average, were found during T2 and T3 and not at T1 or T4.

Conclusions

The researchers noted that the relative effect of working varied throughout the pandemic. Between April 2020 and February 2021, healthcare workers were at an elevated risk of COVID-19 compared to non-essential workers, given that many restrictions were in place during this period. When restrictions were eased later in the pandemic and vaccination began, healthcare workers did not show any increase in the infection risk.

In general, elevated COVID-19 risks were observed among workgroups where employees’ attendance was anticipated during the pandemic. Workers in the food production industry showed no high risks relative to non-essential workers.

These findings revealed that workers in some occupational groups are at higher odds of COVID-19 than others. Although the increased risk for healthcare workers was evident early in the pandemic, it varied with the type of healthcare workers. Elevated risks were noted for workers in the education, and social care sectors post relaxation of restrictions after the first COVID-19 wave, which continued into the third wave highlighting the need to amplify mitigation efforts in the more vulnerable sectors.

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Written by

Tarun Sai Lomte

Tarun is a writer based in Hyderabad, India. He has a Master’s degree in Biotechnology from the University of Hyderabad and is enthusiastic about scientific research. He enjoys reading research papers and literature reviews and is passionate about writing.