COVID-19 mortality attenuated during widespread Omicron transmission, Denmark, 2020 to 2022

BACKGROUND: It sparked considerable attention from international media when Denmark lifted restrictions against COVID-19 in February 2022 amidst widespread transmission of the new SARS-CoV-2 Omicron variant and a steep rise in reported COVID-19 mortality based on the 30-day COVID-19 death count. AIM: Our aim was to investigate how coincidental infections affected COVID-19 mortality estimates following the introduction of the Omicron variant in late 2021. METHODS: We compared the 30-day COVID-19 death count with the observed mortality using three alternative mortality estimation methods; (i) a mathematical model to correct the 30-day COVID-19 death count for coincidental deaths, (ii) the Causes of Death Registry (CDR) and (iii) all-cause excess mortality. RESULTS: There was a substantial peak in the 30-day COVID-19 death count following the emergence of the Omicron variant in late 2021. However, there was also a substantial change in the proportion of coincidental deaths, increasing from 10–20% to around 40% of the recorded COVID-19 deaths. The high number of 30-day COVID-19 deaths was not reflected in the number of COVID-19 deaths in the CDR and the all-cause excess mortality surveillance. CONCLUSION: Our analysis showed a distinct change in the mortality pattern following the introduction of Omicron in late 2021 with a markedly higher proportion of people estimated to have died with, rather than of, COVID-19 compared with mortality patterns observed earlier in the COVID-19 pandemic. Our findings highlight the importance of incorporating alternative mortality surveillance methods to more correctly estimate the burden of COVID-19 as the pandemic continues to evolve

Sociodemographic predictors are associated with compliance to a vaccination-reminder in 9692 girls age 14, Denmark 2014–2015

We aimed to identify sociodemographic predictors of compliance after receiving a personalised reminder on lacking vaccinations against MMR (Measles, Mumps, Rubella) and/or HPV (Human Papilloma Virus) among parents of Danish adolescent girls.A nationwide register-based study, including all 14-year-old girls (15 May 2014–14 May 2015) lacking either MMR, HPV-vaccination or both. Vaccination-compliance following a postal reminder was modelled using multivariable logistic regression and included the following socio-demographic predictors: maternal age, education, employment and ethnicity. Birth order, number of siblings, family-structure, location of residence, and household income.The parents of 9692 girls received a reminder. Out of 4940 exclusively lacking an HPV-vaccine, 15.3% were subsequently vaccinated. Among 2026 only lacking an MMR vaccination, 8.5% were vaccinated. Among 2726 girls lacking both, 5% received an HPV, 4.4% an MMR and 5.4% received both vaccinations. We identified sociodemographic differences between reminderletter-compliers and non-compliers, also according to vaccination types. Non-western descendants were more likely to receive HPV-vaccination, although the association was only significant for those who only lacked HPV (OR 2.02, 95% 1.57–2.59). For girls only lacking an MMR, regional differences were identified. Among girls lacking both vaccines, girls of mothers with intermediate (OR 0.63, 0.42–0.95) or basic education (OR 0.43, 0.24–0.75) were less likely to be vaccinated compared to girls of higher educated mothers.Reminders were in particular effective in increasing HPV uptake among immigrants of non-Western ethnicity. We found reminders to be less effective among less educated mothers whose daughters lacked both vaccines. To increase the coverage in this group, additional interventions are needed. Keywords: Vaccination, Immunization, Socioeconomic factor

Nationwide study on SARS-CoV-2 transmission within households from lockdown to reopening, Denmark, 27 February 2020 to 1 August 2020

BACKGROUND: The COVID-19 pandemic is one of the most serious global public health threats of recent times. Understanding SARS-CoV-2 transmission is key for outbreak response and to take action against the spread of disease. Transmission within the household is a concern, especially because infection control is difficult to apply within this setting. AIM: The objective of this observational study was to investigate SARS-CoV-2 transmission in Danish households during the early stages of the COVID-19 pandemic. METHODS: We used comprehensive administrative register data from Denmark, comprising the full population and all COVID-19 tests from 27 February 2020 to 1 August 2020, to estimate household transmission risk and attack rate. RESULTS: We found that the day after receiving a positive test result within the household, 35% (788/2,226) of potential secondary cases were tested and 13% (98/779) of these were positive. In 6,782 households, we found that 82% (1,827/2,226) of potential secondary cases were tested within 14 days and 17% (371/2,226) tested positive as secondary cases, implying an attack rate of 17%. We found an approximate linear increasing relationship between age and attack rate. We investigated the transmission risk from primary cases by age, and found an increasing risk with age of primary cases for adults (aged ≥ 15 years), while the risk seems to decrease with age for children (aged < 15 years). CONCLUSIONS: Although there is an increasing attack rate and transmission risk of SARS-CoV-2 with age, children are also able to transmit SARS-CoV-2 within the household

Societal activities associated with SARS-CoV-2 infection: a case-control study in Denmark, November 2020.

Identification of societal activities associated with SARS-CoV-2 infection may provide an evidence base for implementing preventive measures. Here, we investigated potential determinants for infection in Denmark in a situation where society was only partially open. We conducted a national matched case-control study. Cases were recent RT-PCR test-positives, while controls, individually matched on age, sex and residence, had not previously tested positive for SARS-CoV-2. Questions concerned person contact and community exposures. Telephone interviews were performed over a 7-day period in December 2020. We included 300 cases and 317 controls and determined odds ratios (ORs) and 95% confidence intervals (95% CI) by conditional logistical regression with adjustment for household size and country of origin. Contact (OR 4.9, 95% CI 2.4-10) and close contact (OR 13, 95% CI 6.7-25) with a person with a known SARS-CoV-2 infection were main determinants. Contact most often took place in the household or work place. Community determinants included events with singing (OR 2.1, 95% CI 1.1-4.1), attending fitness centres (OR 1.8, 95% CI 1.1-2.8) and consumption of alcohol in a bar (OR 10, 95% CI 1.5-65). Other community exposures appeared not to be associated with infection, these included shopping at supermarkets, travel by public transport, dining at restaurants and private social events with few participants. Overall, the restrictions in place at the time of the study appeared to be sufficient to reduce transmission of disease in the public space, which instead largely took place following direct exposures to people with known SARS-CoV-2 infections

Pandemic vaccination strategies and influenza severe outcomes during the influenza A(H1N1)pdm09 pandemic and the post-pandemic influenza season: the Nordic experience.

To access publisher's full text version of this article, please click on the hyperlink in Additional Links field or click on the hyperlink at the top of the page marked DownloadDuring the 2009/10 influenza A(H1N1)pdm09 pandemic, the five Nordic countries adopted different approaches to pandemic vaccination. We compared pandemic vaccination strategies and severe influenza outcomes, in seasons 2009/10 and 2010/11 in these countries with similar influenza surveillance systems. We calculated the cumulative pandemic vaccination coverage in 2009/10 and cumulative incidence rates of laboratory confirmed A(H1N1)pdm09 infections, intensive care unit (ICU) admissions and deaths in 2009/10 and 2010/11. We estimated incidence risk ratios (IRR) in a Poisson regression model to compare those indicators between Denmark and the other countries. The vaccination coverage was lower in Denmark (6.1%) compared with Finland (48.2%), Iceland (44.1%), Norway (41.3%) and Sweden (60.0%). In 2009/10 Denmark had a similar cumulative incidence of A(H1N1)pdm09 ICU admissions and deaths compared with the other countries. In 2010/11 Denmark had a significantly higher cumulative incidence of A(H1N1)pdm09 ICU admissions (IRR: 2.4; 95% confidence interval (CI): 1.9-3.0) and deaths (IRR: 8.3; 95% CI: 5.1-13.5). Compared with Denmark, the other countries had higher pandemic vaccination coverage and experienced less A(H1N1)pdm09-related severe outcomes in 2010/11. Pandemic vaccination may have had an impact on severe influenza outcomes in the post-pandemic season. Surveillance of severe outcomes may be used to compare the impact of influenza between seasons and support different vaccination strategies

Changing rates but persisting seasons: patterns of enterovirus infections in hospitalizations and outpatient visits in Denmark 2015-2022

BackgroundEnteroviruses (EV) constitute a diverse group of viruses manifesting a broad spectrum of clinical presentations in humans ranging from mild skin manifestations to more severe central nervous system (CNS) infection. Severe infections are reported with increased frequency globally, albeit the burden of diseases and the evolution of circulating viruses is largely unknown. We aimed to systematically explore contemporary trends in hospitalizations attributed to EV infections using national hospitalization discharge data.MethodsWe utilized the Danish National Patient Register which holds information on all contacts to Danish hospitals. We covered eight full years (2015-2022). Length-of-stay and administrative procedure codes were used to distinguish hospital admissions from outpatient visits. We utilized burden of disease estimates and distribution statistics.ResultsWe identified 1029 hospitalizations and 1970 outpatient visits due to EV infections. The hospital admissions were primarily associated with CNS-infections (n=570, 55.4%) and skin (n=252, 24.5%), with variation over the studied period. The admitted patients were predominately children (43.8%) though patients were identified in all ages. The clinical manifestation was associated with age, with CNS infections dominating in the neonates and adults, and skin infections dominating in children 1-2 years (17.2%). Outpatient visits were predominantly observed among children 1-2 years (55.0%), presenting with skin symptoms (77.9%). We show a seasonal pattern of EV infections with summer/fall peaks and markedly impact on the EV hospitalization burden related to COVID-19 mitigation measures including national lockdown periods. 25% of hospital admissions occurred during 2020-2022.ConclusionEV infections caused both hospital admissions and outpatient visits in the period studied, predominately among children aged 1-2 years. Overall, skin infections dominated the outpatient visits, while the majority of hospital admissions were due to CNS infections. The pandemic period did not change the seasonal pattern of EV infections but notably lowered the number of admissions to hospital with CNS infection and raised the number of outpatient admissions with skin infection

A standardised protocol for assessment of relative SARS-CoV-2 variant severity, with application to severity risk for COVID-19 cases infected with Omicron BA.1 compared to Delta variants in six European countries

Several SARS-CoV-2 variants that evolved during the COVID-19 pandemic have appeared to differ in severity, based on analyses of single-country datasets. With decreased SARS-CoV-2 testing and sequencing, international collaborative studies will become increasingly important for timely assessment of the severity of newly emerged variants. The Joint WHO Regional Office for Europe and ECDC Infection Severity Working Group was formed to produce and pilot a standardised study protocol to estimate relative variant case-severity in settings with individual-level SARS-CoV-2 testing and COVID-19 outcome data during periods when two variants were co-circulating. To assess feasibility, the study protocol and its associated statistical analysis code was applied by local investigators in Denmark, England, Luxembourg, Norway, Portugal and Scotland to assess the case-severity of Omicron BA.1 relative to Delta cases. After pooling estimates using meta-analysis methods (random effects estimates), the risk of hospital admission (adjusted hazard ratio [aHR]=0.41, 95% CI 0.31-0.54), ICU admission (aHR=0.12, 95% CI 0.05-0.27), and death (aHR=0.31, 95% CI 0.28-0.35) was lower for Omicron BA.1 compared to Delta cases. The aHRs varied by age group and vaccination status. In conclusion, this study has demonstrated the feasibility of conducting variant severity analyses in a multinational collaborative framework. The results add further evidence for the reduced severity of the Omicron BA.1 variant.Comment: 21 pages, 6 figures (excluding supplementary material

Long-term detection of SARS-CoV-2 antibodies after infection and risk of re-infection

OBJECTIVES: To evaluate long-term sensitivity for detection of total antibodies against SARS-CoV-2 METHODS: From week 41, 2020, through week 26, 2021, all Danish blood donations were tested for SARS-CoV-2 antibodies with the Wantai assay. The results were linked with polymerase chain reaction (PCR) test results from the Danish Microbiological Database (MiBa). RESULTS: During the study period, 105,646 non-vaccinated Danish blood donors were tested for SARS-CoV-2 antibodies, and 3,806 (3.6%) had a positive PCR test before the blood donation. Among the donors with a positive PCR test, 94.2% subsequently also had a positive antibody test. The time between the positive PCR test and the antibody test was up to 15 months and there was no evidence of a decline in proportion with detectable antibodies over time. A negative serological result test was associated with a higher incidence of re-infection (Incidence Rate Ratio = 0.102 (95% confidence interval (CI): 0.039–0.262)). CONCLUSION: Among healthy blood donors, 94.2% developed SARS-CoV-2 antibodies after infection, and a lack of detectable antibodies was associated with re-infection