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Espenhain L, Ethelberg S, Mortensen LH, Christiansen LE. Automated local lockdowns for SARS-CoV-2 epidemic control-assessment of effect by controlled interrupted time series analysis. IJID REGIONS 2024; 12:100380. [PMID: 38911235 PMCID: PMC11186853 DOI: 10.1016/j.ijregi.2024.100380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/18/2024] [Revised: 05/22/2024] [Accepted: 05/22/2024] [Indexed: 06/25/2024]
Abstract
Objectives During the COVID-19 pandemic, broad non-pharmaceutical interventions such as national lockdowns were effective but had significant drawbacks, prompting targeted approaches, such as Denmark's localized lockdowns, based on specific epidemiological criteria. This study evaluates the effect of Denmark's automated local lockdown strategy on epidemic control to inform future response. Methods This was a register-based controlled interrupted time series analysis, examining SARS-CoV-2 infection rates in Danish parishes from March to September 2021. The matching of control parishes was based on location, time, and pre-lockdown infection trends, with the lockdown's start defined as the day after a parish exceeded the lockdown criteria. Follow-up included 3-week pre-lockdown and 2-week post-lockdown. Results A total of 30 parishes were mandated to lockdown, approximately 3.5% of the population of Denmark. A total of 94 control parishes were used as 109 controls. The decrease in the incidence during the 2-week follow-up period after the initiation of the lockdown was 13% points higher in case parishes: in case parishes, the incidence was reduced by 78% compared with 65% in control parishes. Conclusions Our findings demonstrate that local lockdowns did have a positive effect in mitigating the spread of the SARS-CoV-2 virus, making them valuable in the fight against the COVID-19 pandemic and an important alternative to national lockdowns.
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Affiliation(s)
- Laura Espenhain
- Department of Infectious Disease epidemiology and Prevention, Statens Serum Institut, Copenhagen, Denmark
| | - Steen Ethelberg
- Department of Infectious Disease epidemiology and Prevention, Statens Serum Institut, Copenhagen, Denmark
- Department of Public Health, University of Copenhagen, Copenhagen, Denmark
| | - Laust Hvas Mortensen
- Department of Public Health, University of Copenhagen, Copenhagen, Denmark
- Statistics Denmark, Copenhagen, Denmark
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Johannesen N, Tang-Andersen Martinello A, Meyer BB, Vestergaard ET, Andersen AL, Jensen TL. Substantial transmission of SARS-CoV-2 through casual contact in retail stores: Evidence from matched administrative microdata on card payments and testing. Proc Natl Acad Sci U S A 2024; 121:e2317589121. [PMID: 38630715 PMCID: PMC11047087 DOI: 10.1073/pnas.2317589121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Accepted: 03/21/2024] [Indexed: 04/19/2024] Open
Abstract
This paper presents quasiexperimental evidence of Covid-19 transmission through casual contact between customers in retail stores. For a large sample of individuals in Denmark, we match card payment data, indicating exactly where and when each individual made purchases, with Covid-19 test data, indicating when each individual was tested and whether the test was positive. The resulting dataset identifies more than 100,000 instances where an infected individual made a purchase in a store and, in each instance, allows us to track the infection dynamics of other individuals who made purchases in the same store around the same time. We estimate transmissions by comparing the infection rate of exposed customers, who made a purchase within 5 min of an infected individual, and nonexposed customers, who made a purchase in the same store 16 to 30 min before. We find that exposure to an infected individual in a store increases the infection rate by around 0.12 percentage points (P < 0.001) between day 3 and day 7 after exposure. The estimates imply that transmissions in stores contributed around 0.04 to the reproduction number for the average infected individual and significantly more in the period where Omicron was the dominant variant.
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Affiliation(s)
- Niels Johannesen
- Saïd Business School, Oxford University, OxfordOX1 1HP, United Kingdom
- Department of Economics, University of Copenhagen, CopenhagenK 1353, Denmark
- Center for Economic Behavior and Inequality, University of Copenhagen, CopenhagenK 1353, Denmark
| | | | | | | | - Asger Lau Andersen
- Department of Economics, University of Copenhagen, CopenhagenK 1353, Denmark
- Center for Economic Behavior and Inequality, University of Copenhagen, CopenhagenK 1353, Denmark
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Rosner BM, Falkenhorst G, Kumpf I, Enßle M, Hicketier A, Dörre A, Stark K, Wilking H. Case-control study of behavioural and societal risk factors for sporadic SARS-CoV-2 infections, Germany, 2020-2021 (CoViRiS study). Epidemiol Infect 2024; 152:e16. [PMID: 38220467 PMCID: PMC10894885 DOI: 10.1017/s0950268824000050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Revised: 12/14/2023] [Accepted: 12/18/2023] [Indexed: 01/16/2024] Open
Abstract
During the COVID-19 pandemic in Germany, a variety of societal activities were restricted to minimize direct personal interactions and, consequently, reduce SARS-CoV-2 transmission. The aim of the CoViRiS study was to investigate whether certain behaviours and societal factors were associated with the risk of sporadic symptomatic SARS-CoV-2 infections. Adult COVID-19 cases and frequency-matched population controls were interviewed by telephone regarding activities that involved contact with other people during the 10 days before illness onset (cases) or before the interview (controls). Associations between activities and symptomatic SARS-CoV-2 infection were analysed using logistic regression models adjusted for potential confounding variables. Data of 859 cases and 1 971 controls were available for analysis. The risk of symptomatic SARS-CoV-2 infection was lower for individuals who worked from home (adjusted odds ratio (aOR) 0.5; 95% confidence interval (CI) 0.3-0.6). Working in a health care setting was associated with a higher risk (aOR: 1.5; 95% CI: 1.1-2.1) as were private indoor contacts, personal contacts that involved shaking hands or hugging, and overnight travelling within Germany. Our results are in line with some of the public health recommendations aimed at reducing interpersonal contacts during the COVID-19 pandemic.
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Affiliation(s)
- Bettina M Rosner
- Department of Infectious Disease Epidemiology, Robert Koch Institute, Berlin, Germany
| | - Gerhard Falkenhorst
- Department of Infectious Disease Epidemiology, Robert Koch Institute, Berlin, Germany
| | - Isabella Kumpf
- Department of Infectious Disease Epidemiology, Robert Koch Institute, Berlin, Germany
| | - Maren Enßle
- Department of Infectious Disease Epidemiology, Robert Koch Institute, Berlin, Germany
| | - Andreas Hicketier
- Department of Infectious Disease Epidemiology, Robert Koch Institute, Berlin, Germany
| | - Achim Dörre
- Department of Infectious Disease Epidemiology, Robert Koch Institute, Berlin, Germany
| | - Klaus Stark
- Department of Infectious Disease Epidemiology, Robert Koch Institute, Berlin, Germany
| | - Hendrik Wilking
- Department of Infectious Disease Epidemiology, Robert Koch Institute, Berlin, Germany
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Benedetti G, Holm Hansen C, Tølbøll Svendsen A, Grimstrup Joensen K, Sørensen G, Engsbro AL, Torpdahl M, Møller Nielsen E, Ethelberg S. The effect of changing diagnostic method from culture to PCR on the number of episodes of human campylobacteriosis in Denmark: a retrospective study (2015-2022). Microbiol Spectr 2024; 12:e0341823. [PMID: 38063356 PMCID: PMC10783023 DOI: 10.1128/spectrum.03418-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Accepted: 11/13/2023] [Indexed: 01/13/2024] Open
Abstract
IMPORTANCE This study is important because it shows the potential epidemiological silence associated with the use of culture as the primary diagnostic method for the laboratory identification of human campylobacteriosis. Also, we show how polymerase chain reaction methods are associated with a systematic increase in the number of human campylobacteriosis episodes as reported by routine disease surveillance. These findings are operationally relevant and have public health implications because they tell how crucial it is to consider changes in diagnostic methods, e.g., in the epidemiological analysis of historical data and in the interpretation of future data in light of the past. We also believe that this study highlights how the synergy between microbiology and epidemiology is essential for disease surveillance.
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Affiliation(s)
- Guido Benedetti
- Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Copenhagen, Denmark
| | - Christian Holm Hansen
- Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Copenhagen, Denmark
| | - Anna Tølbøll Svendsen
- Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Copenhagen, Denmark
- Department of Medicine, Zealand University Hospital, Køge, Denmark
- Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
| | | | - Gitte Sørensen
- Department of Bacteria, Parasites and Fungi, Statens Serum Institut, Copenhagen, Denmark
| | - Anne Line Engsbro
- Department of Clinical Microbiology, Zealand University Hospital, Slagelse, Denmark
- Hvidovre University Hospital, Hvidovre, Denmark
| | - Mia Torpdahl
- Department of Bacteria, Parasites and Fungi, Statens Serum Institut, Copenhagen, Denmark
| | - Eva Møller Nielsen
- Department of Bacteria, Parasites and Fungi, Statens Serum Institut, Copenhagen, Denmark
| | - Steen Ethelberg
- Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Copenhagen, Denmark
- Department of Public Health, Global Health Section, University of Copenhagen, Copenhagen, Denmark
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Gram MA, Steenhard N, Cohen AS, Vangsted AM, Mølbak K, Jensen TG, Hansen CH, Ethelberg S. Patterns of testing in the extensive Danish national SARS-CoV-2 test set-up. PLoS One 2023; 18:e0281972. [PMID: 37490451 PMCID: PMC10368237 DOI: 10.1371/journal.pone.0281972] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Accepted: 07/12/2023] [Indexed: 07/27/2023] Open
Abstract
BACKGROUND The Danish national SARS-CoV-2 mass test system was among the most ambitious worldwide. We describe its set-up and analyse differences in patterns of testing per demography and time period in relation to the three waves of SARS-CoV-2 transmission in Denmark. METHODS We included all reported PCR- and rapid antigen-tests performed between 27 February 2020 and 10 March 2022 among all residents aged 2 years or above. Descriptive statistics and Poisson regression models were used to analyse characteristics of individuals tested for SARS-CoV-2 using a national cohort study design. RESULTS A total of 63.7 million PCR-tests and 60.0 million rapid antigen-tests were performed in the study period, testing 90.9% and 78.8% of the Danish population at least once by PCR or antigen, respectively. Female sex, younger age, Danish heritage and living in the capital area were all factors positively associated with the frequency of PCR-testing. The association between COVID-19 vaccination and PCR-testing changed from negative to positive over time. CONCLUSION We provide details of the widely available, free-of-charge, national SARS-CoV-2 test system, which served to identify infected individuals, assist isolation of infectious individuals and contact tracing, and thereby mitigating the spread of SARS-CoV-2 in the Danish population. The test system was utilized by nearly the entire population at least once, and widely accepted across different demographic groups. However, demographic differences in the test uptake did exist and should be considered in order not to cause biases in studies related to SARS-CoV-2, e.g., studies of transmission and vaccine effectiveness.
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Affiliation(s)
- Mie Agermose Gram
- Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Copenhagen S, Denmark
| | - Nina Steenhard
- TestCentre Denmark, Statens Serum Institut, Copenhagen S, Denmark
| | | | | | - Kåre Mølbak
- Division of Infectious Disease Preparedness, Statens Serum Institut, Copenhagen S, Denmark
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark
| | - Thøger Gorm Jensen
- Department of Clinical Microbiology, Odense University Hospital Odense C, Odense, Denmark
- Research Unit of Clinical Microbiology, University of Southern Denmark, Odense, Denmark
| | - Christian Holm Hansen
- Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Copenhagen S, Denmark
| | - Steen Ethelberg
- Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Copenhagen S, Denmark
- Department of Public Health, Global Health Section, University of Copenhagen, Copenhagen K, Denmark
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Krogsgaard LW, Espenhain L, Tribler S, Sværke Jørgensen C, Hansen CH, Møller FT, Glode Helmuth I, Sönksen UW, Vangsted AM, Ullum H, Ethelberg S. Seroprevalence of SARS-CoV-2 Antibodies in Denmark: Results of Two Nationwide Population-Based Surveys, February and May 2021. Infect Drug Resist 2023; 16:301-312. [PMID: 36683911 PMCID: PMC9851711 DOI: 10.2147/idr.s383491] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Accepted: 12/14/2022] [Indexed: 01/15/2023] Open
Abstract
Background Seroprevalence studies can be used to measure the progression of national COVID-19 epidemics. The Danish National Seroprevalence Survey of SARS-CoV-2 infections (DSS) was conducted as five separate surveys between May 2020 and May 2021. Here, we present results from the two last surveys conducted in February and May 2021. Methods Persons aged 12 or older were randomly selected from the Danish Population Register and those having received COVID-19 vaccination subsequently excluded. Invitations to have blood drawn in local test centers were sent by mail. Samples were analyzed for whole Immunoglobulin by ELISA. Seroprevalence was estimated by sex, age and geography. Comparisons to vaccination uptake and RT-PCR test results were made. Results In February 2021, we found detectable antibodies in 7.2% (95% CI: 6.3-7.9%) of the invited participants (participation rate 25%) and in May 2021 in 8.6% (95% CI: 7.6-9.5%) of the invited (participation rate: 14%). Seroprevalence did not differ by sex, but by age group, generally being higher among the <50 than 50+ year-olds. In May 2021, levels of seroprevalence varied from an estimated 13% (95% CI: 12-15%) in the capital to 5.2% (95% CI: 3.4-7.4%) in rural areas. Combining seroprevalence results with vaccine coverage, estimates of protection against infection in May 2021 varied from 95% among 65+ year-olds down to 10-20% among 12-40 year-olds. In March-May 2021, an estimated 80% of all community SARS-CoV-2 infections were diagnosed by RT-PCR and captured by surveillance. Conclusion Seroprevalence estimates doubled during the 2020-21 winter wave of SARS-CoV-2 infections and then stabilized as vaccinations were rolled out. The epidemic affected large cities and younger people the most. Denmark saw comparatively low infections rates, but high test coverage; an estimated four out of five infections were detected by RT-PCR in March-May 2021.
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Affiliation(s)
- Lene Wulff Krogsgaard
- Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Copenhagen, Denmark
| | - Laura Espenhain
- Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Copenhagen, Denmark
| | - Siri Tribler
- Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Copenhagen, Denmark
| | | | - Christian Holm Hansen
- Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Copenhagen, Denmark
| | - Frederik Trier Møller
- Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Copenhagen, Denmark
| | - Ida Glode Helmuth
- Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Copenhagen, Denmark
| | - Ute Wolff Sönksen
- Department of Bacteria, Parasites and Fungi, Statens Serum Institut, Copenhagen, Denmark,TestCentre Denmark, Statens Serum Institut, Copenhagen, Denmark
| | | | - Henrik Ullum
- Division of Infectious Disease Preparedness, Statens Serum Institut, Copenhagen, Denmark
| | - Steen Ethelberg
- Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Copenhagen, Denmark,Department of Public Health, University of Copenhagen, Copenhagen, Denmark,Correspondence: Steen Ethelberg, Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, 5 Artillerivej, 2300 Copenhagen, Denmark, Tel +45 3268 3545, Email
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