The Corona virus disease (Covid-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has to date led to more than 3.5 million deaths and over 170 million confirmed cases worldwide.1 Therefore, vaccine development has been of highest priority. Late 2020, the first Covid-19 vaccines were approved and used in the US, but on a worldwide level, there is ongoing shortage of vaccines and knowledge regarding vaccine prioritization for high-risk groups are warranted. Studies have indicated high numbers of Covid-19 positive tests among healthcare professionals.2, 3, 4, 5, 6 A recent Journal of Infection publication showed that home- or healthcare personnel from six UK-based hospitals were more likely to be tested positive for Covid-19 compared to the general population.6
Home- and healthcare workers are an essential part of the healthcare system and reducing potential infection transmission in this setting would be beneficial to maintain a sufficient and effective healthcare system, alongside reducing transmission risk to citizens, patients and family members. With ongoing shortage of vaccines, prioritization is needed to reduce transmission risk to vulnerable patients and citizens to lower Covid-19 related morbidity and mortality. However, knowledge on the risk of Covid-19 in home- or healthcare personnel compared to the background population is lacking but essential.
This nationwide register-based study of risk of Covid-19 contraction and severe infection in relation to home- or healthcare professional status identified all residents in Denmark between aged 25–65 and alive on February 1st, 2020. Home- or healthcare professional status was available from education and employment registries until January 31st, 2020. The civil personal registration number (CPR) was used to link registry data. Data on patient age, sex, migration, Danish native versus non-native (immigrant or descendant) residency and cohabitation status were derived from the Danish Civil Registration System. Comorbidities were assessed from International Classification of Disease version 10 (ICD-10) diagnoses registered in the Danish National Patient Register including hypertension, diabetes, obesity, sleep apnea, chronic obstructive pulmonary disease (COPD), previous myocardial infarction (MI), ischemic heart disease (IHD), heart failure, stroke, peripheral vascular disease, rheumatic disease, chronic kidney disease, and malignant disease. From the Danish Prescription Registry, we defined hypertension when at least two antihypertensive drug prescriptions were filled in two consecutive 100-day periods prior to Covid-19 diagnosis. Diabetes and COPD were defined as a prescription fill for a relevant antidiabetic drug or relevant inhalation medication (anticholinergic alone or in combination with long-acting beta-2 agonist) no later than one year before Covid-19, or a relevant diagnosis code in the Danish National Patient Register any time before Covid-19. As a measure of socioeconomic position, information on equivalized income based on a modified scale from the Organization for Economic Cooperation and Development (OECD) to ensure comparability between different household sizes, were assessed from Statistics Denmark and aggregated from quartiles of equivalized household income levels within the following age groups; 25–34, 35–44, 45–54, and 55–65.
Outcomes were 1) Covid-19 contraction defined as positive PCR test, 2) Covid-19 severe infection defined as composite of severe diagnosis (specific ICD-10 code B972A), intensive care unit (ICU) admission or death within 30 days after positive Covid-19 test, and 3) individual endpoints of ICU admission and death. Individuals were followed until outcome of interest, non-Covid-19 death or October 28, 2020, whichever came first. Multivariable Cox regression was performed to assess absolute risks and risk ratios for outcomes, standardized to the age, sex, equivalized income, native versus non-native residency status and comorbidity distribution of all patients.
Of approximately 5.8 million Danes, we identified (N = 3063,127) aged 25–65 and excluded 37,626 due to missing education or employment status, leaving 3024,501 as the study population; 512,145 (16.9%) were home- or healthcare professionals. Between February 1st, 2020, and October 28th, 2020, 24,757 were tested positive for Covid-19; 6793 (27.4%) were home- or healthcare professionals. Baseline characteristics are displayed in Table 1 .
Table 1.
Baseline characteristics by home- or healthcare professional status.
| Home- or healthcare professional | Non-home or healthcare professional | ||
|---|---|---|---|
| Variable | N = 512,145 | N = 2512,356 | P-value |
| Age (years), median [Q1-Q3] | 47 [36–56] | 45 [34–55] | < 0.001 |
| Age 25–34 years, n (%) | 115,159 (22.5) | 637,023 (25.4) | |
| Age 35–44 years, n (%) | 114,153 (22.3) | 564,000 (22.4) | |
| Age 45–54 years, n (%) | 130,896 (25.6) | 663,869 (26.4) | |
| Age 55–65 years, n (%) | 151,937 (29.7) | 647,464 (25.8) | < 0.001 |
| Female sex, n (%) | 424,330 (82.9) | 1077,275 (42.9) | < 0.001 |
| Equivalized income group 0, n (%) | 105,918 (20.7) | 642,408 (25.7) | |
| Equivalized income group 1, n (%) | 148,496 (29.0) | 596,355 (23.9) | |
| Equivalized income group 2, n (%) | 141,121 (27.6) | 609,642 (24.4) | |
| Equivalized income group 3, n (%) | 116,219 (22.7) | 646,757 (25.9) | < 0.001 |
| missing | 391 | 17,194 | |
| Equivalized income (EUR), median [Q1-Q3] | 35,951 [27,746–46,376] | 35,761 [25,108–47,702] | < 0.001 |
| missing | 391 | 17,194 | |
| Non-native residency status, n (%) | 58,481 (11.4) | 426,767 (17.0) | < 0.001 |
| Living alone, n (%) | 156,557 (30.6) | 858,074 (34.2) | < 0.001 |
| Diabetes, n (%) | 9307 (1.8) | 65,179 (2.6) | < 0.001 |
| Hypertension, n (%) | 53,237 (10.4) | 239,030 (9.5) | < 0.001 |
| Obesity, n (%) | 1864 (0.4) | 5543 (0.2) | < 0.001 |
| Sleep apnea, n (%) | 2507 (0.5) | 18,671 (0.7) | < 0.001 |
| COPD, n (%) | 4799 (0.9) | 23,727 (0.9) | 0.62 |
| Prior myocardial infarction, n (%) | 127 (0.0) | 1044 (0.0) | < 0.001 |
| Ischemic heart disease, n (%) | 732 (0.1) | 5124 (0.2) | < 0.001 |
| Heart failure, n (%) | 511 (0.1) | 3857 (0.2) | < 0.001 |
| Stroke, n (%) | 227 (0.0) | 1404 (0.1) | 0.001 |
| Peripheral artery disease, n (%) | 55 (0.0) | 330 (0.0) | 0.19 |
| Rheumatic disease, n (%) | 2858 (0.6) | 9193 (0.4) | < 0.001 |
| Chronic kidney disease, n (%) | 1056 (0.2) | 6542 (0.3) | < 0.001 |
| Prior malignant disease, n (%) | 6963 (1.4) | 25,629 (1.0) | < 0.001 |
Q1-Q3, 1st to 3rd quartiles; n, number; EUR, euros; COPD, chronic obstructive pulmonary disease. Non-native residency status refers to immigrant or descendant of immigrant, as opposed to Danish native residency status. The four equivalized income groups are based on aggregated quartiles of equivalized household income levels within the following age groups (25–34, 35–44, 45–54, 55–65 years), with group 0 being the lowest income group and group 4 the highest.
Results are displayed in Fig 1 . Standardized absolute risk for Covid-19 contraction was significantly higher for home- or healthcare professionals versus controls, with 1.4% [95%CI 1.4–1.5] versus 0.7% [95%CI 0.7–0.7], P<0.001. The standardized relative risk (RR) was 2.06 [95%CI 2.00–2.12]. Standardized absolute risk of severe Covid-19 infection was 0.1% for home- or healthcare professionals versus 0.1% for controls, RR 0.86 [95%CI 0.77–0.94]. Among the 24,757 subjects diagnosed with Covid-19, the absolute risk for severe infection was insignificant, with 1.3% [95%CI 1.1–1.5] versus 1.0% [95%CI 0.8–1.3], and the corresponding relative risk was 0.79 [95%CI 0.55–1.03].
Fig. 1.
Forest plot displaying the relative risks of contraction and severe infection measures for non- versus home- or healthcare professionals.
Several studies have addressed the occupational hazard of Covid-19 disease in home- or healthcare professionals but only few had the possibility to compare the risk to the general population.2, 3, 4, 5, 6 One study documented a significantly higher hospitalization rate for Covid-19 infected healthcare workers relative to Covid-19 positive population controls.5 Another study based on point-prevalence of PCR-positive Covid-19 tests indicated significantly higher Covid-19 risk among healthcare workers from six UK-based hospitals in comparison to the general population.6 We found a significantly higher Covid-19 contraction risk of approximately two-fold that of the general population among home- or healthcare professionals. Adding to current literature, we showed that the elevated risk of Covid-19 contraction did not translate into a higher risk of severe Covid-19 disease trajectory. However, we are not able to report long-term functional impairment related to Covid-19. As such, our study cannot be used to conclude that healthcare professionals suffer no severe Covid-19 related sequalae, as more studies examining both short- and long-term outcomes of function following Covid-19 are warranted. The increased risk of Covid-19 contraction supports that Covid-19 can be viewed as an occupational hazard for home- and healthcare workers and stresses the importance of adequate protection and vaccination. Our study findings support that the working age population of home- and healthcare workers should have a high priority for vaccine distribution.
In conclusion, home- or healthcare professionals had significantly higher Covid-19 contraction risk but not severe infection risk. Since our study indicates a significantly elevated risk of Covid-19 contraction among home- and healthcare professionals and issues with vaccine shortage remains, it is important to prioritize Covid-19 vaccination of home- and healthcare professionals.
Declaration of Competing Interest
Lars Køber reports personal fees from Speakers honorarium from Novo, Novartis, AstraZeneca and Boehringer outside the submitted work. Christian Torp-Pedersen reports grants from Bayer, grants from Novo Nordisk outside the submitted work. All other authors have nothing to declare.
Acknowledgments
Acknowledgment
The authors would like to extend their gratitude towards Jørn Korsbø Pedersen and his colleagues at Statistics Denmark for their excellent help in relation data accessibility. Further the authors acknowledge The Danish Departments of Clinical Microbiology and Statens Serum Institut for carrying out laboratory analysis, registration, and release of the national SARS-CoV-2 surveillance data for the present study.
Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Data statement
The dataset generated during the current study is not publicly available. All data were accessed in the research environment of Statistics Denmark where multiple registries can be combined with the limitation that individual data cannot be exported from the research environment. Further, individual information is encrypted. Thus, datasets cannot be made available. Other researchers that wish to access the data and codes can contact the authors of this study for collaboration on further studies.
References
- 1.World Health Organization. WHO coronavirus disease (COVID-19) dashboard. 2021. https://covid19.who.int. Accessed 2 June 2021.
- 2.Gómez-Ochoa S.A., Franco O.H., Rojas L.Z., Raguindin P.F., Roa-Díaz Z.M., Wyssmann B.M. COVID-19 in healthcare workers: a living systematic review and meta-analysis of prevalence, risk factors, clinical characteristics, and outcomes. Am J Epidemiol. 2021;190:161–175. doi: 10.1093/aje/kwaa191. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Iversen K., Bundgaard H., Hasselbalch R.B., Kristensen J.H., Nielsen P.B., Pries-Heje M. Risk of COVID-19 in health-care workers in Denmark: an observational cohort study. Lancet Infect Dis. 2020;20:1401–1408. doi: 10.1016/S1473-3099(20)30589-2. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Nguyen L.H., Drew D.A., Graham M.S., Joshi A.D., Guo C.G., Ma W. Risk of COVID-19 among front-line health-care workers and the general community: a prospective cohort study. Lancet Public Health. 2020;5:e475–e483. doi: 10.1016/S2468-2667(20)30164-X. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.Shah A.S.V., Wood R., Gribben C., Caldwell D., Bishop J., Weir A. Risk of hospital admission with coronavirus disease 2019 in healthcare workers and their households: nationwide linkage cohort study. BMJ. 2020;371:m3582. doi: 10.1136/bmj.m3582. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Brown C.S., Clare K., Chand M., Andrews J., Auckland C., Beshir S. Snapshot PCR surveillance for SARS-CoV-2 in hospital staff in England. J Infect. 2020;81(3):427–434. doi: 10.1016/j.jinf.2020.06.069. Sep. [DOI] [PMC free article] [PubMed] [Google Scholar]