In this register study, we found an incidence rate of 1.48 % for confirmed SARS-CoV-2 among health service staff in Norway in 2020. The incidence varied between sex, age, country of birth and place of residence, but also between different occupational groups and within different parts of the health service. As with the general population, the number of positive cases among health service staff rose in the post-summer period, but a peak was also seen for this group in the early stages of the pandemic.
Health service employees are a heterogeneous group with differing characteristics that can impact on their level of non-work-related risk of being diagnosed with SARS-CoV-2. This can include infection transmission from close contacts outside work, which has also been shown to be a key factor in the incidence among healthcare personnel (8). The majority of positive cases in Norway relate to people who were infected by household members, and only about one-sixth are transmitted at work or university (1). Structural and social inequalities have been shown to be associated with increased transmission rates and severity of disease (18–20). The transmission rate and hospital admission rates are higher among people born outside Norway (8, 21). In the early stages of the pandemic, the higher proportions of infections that were imported among dentists, psychologists and doctors may indicate that transmission has a positive correlation with socio-economic status and mobility. The high incidence among the youngest age group and people born in low- and middle-income countries suggests that transmission is more likely to take place outside the workplace and should be compared with similar patterns in the rest of the population (1).
Possible work-related risks of infection may be associated with particular types of work, such as patient-centred tasks that entail exposure to SARS-CoV-2, either from COVID-19 patients or patients with an unknown infection status, or with other variations in working practices in the different parts of the health service. Differences in physical working conditions and opportunities for social distancing can impact on the work-related risk, since it is known that those who are pre- and asymptomatic are contagious. Evidence has been found of nosocomial transmission to and between employees during SARS-CoV-2 outbreaks in Norway (22–24). Access to PPE and training in correct use can also impact on the risk level. Lack of PPE is associated with an increased risk of COVID-19 in healthcare personnel (7). In Norway, shortfalls in local supplies of PPE were reported at the start of the pandemic (25), but the national supply gradually reached an adequate level (26). Any potential work-related risk is impacted by the community transmission risk.
Magnusson et al. found that the proportion of doctors, nurses, dentists and physiotherapists with confirmed SARS-CoV-2 was higher than in other occupational groups in the early stages of the pandemic, but no such disparity was found for the second period (July–December) (3). During the first six weeks, approximately 2 % of the population in Norway was tested for SARS-CoV-2 (approximately 120 000 tests), and 5 % of these tests were positive (27). Health service staff accounted for about a quarter of all tests during this period (about 30 000), and about 3 % of these were positive (Figure 3). In order not to exceed the test capacity, health service staff who have close contact with patients were prioritised for testing early in the pandemic (28). This prioritisation may have contributed to more confirmed infections for this group.
Our data show that doctors were tested more frequently than the other occupational groups. Ambulance personnel, nursing associates, healthcare assistants and cleaners are groups that were tested less. However, these groups have a relatively high proportion of positive tests, which may imply higher undiagnosed infection among these groups. We know that staff can transmit the infection to patients and residents. Escalating the testing activity for these large occupational groups could potentially prevent infection transmission in the health service. The high incidence among ambulance personnel is concerning, as it appears to be high irrespective of various other characteristics. However, it may also be coincidental, as the study population for this group is small.
We found a higher incidence of confirmed infections among staff in acute hospitals and nursing homes than other parts of the health service. Infection rates among acute hospital staff may be related to the fact that the majority of such hospitals are located in cities with widespread community transmission. In nursing homes, the incidence should be considered in conjunction with the numerous major outbreaks of nosocomial transmission to and between staff (23, 24), but also with the composition of occupational groups, age distribution and socio-economic factors. We find higher confirmed infection among cleaners and staff born in low- and middle-income countries. It has also been previously reported that cleaners are an overrepresented group (8).
In this large register study, we have shown the prevalence of confirmed SARS-CoV-2 among health service staff in Norway at an overarching level. The number of confirmed cases has been relatively low in Norway, which in turn means incidences are low in many occupational groups and must therefore be interpreted with caution. We have not performed analyses that compare groups, and the data material in Beredt C19 is not suited to further breakdowns by occupational groups or industrial classifications for examining different specialties or departments that could be assumed to be particularly at risk of infection. This study can thus not provide an answer to whether occupational practice is associated with an increased risk of SARS-CoV-2 infection.
A weakness of our study is that data for testing activity before 1 April are incomplete and of a relatively low quality, which means that we have underestimated the incidence and testing rates in the first four weeks. The data sources in the study also have some weaknesses. For example, the Aa Register does not include self-employed persons. If these had been included, it may have changed the number of confirmed infections among staff in parts of the primary health service, but we do not know in which direction. We included health service employees even where this was not their main job, which may have been outside the health service. This means that our population is somewhat larger than that used in other statistics. We did not have data on income, and some of the employees may have been inactive.
This study has shown that the incidence of confirmed infections differs among health service staff. It is important to shed light on this in order to be able to evaluate infection control measures and target efforts to prevent transmission in the health service. However, more research is needed to establish whether, and to what extent, infection among staff is linked to exposure from occupational practice in the health service in Norway.