Seroprevalence and infection fatality rate of the SARS-CoV-2 Omicron variant in Denmark: A nationwide serosurveillance study

Erikstrup, Christian; Laksafoss, Anna Damkjær; Gladov, Josephine; Kaspersen, Kathrine Agergård; Mikkelsen, Susan; Hindhede, Lotte; Boldsen, Jens Kjærgaard; Jørgensen, Signe Winther; Ethelberg, Steen; Holm, Dorte Kinggaard; Bruun, Mie Topholm; Nissen, Janna; Schwinn, Michael; Brodersen, Thorsten; Mikkelsen, Christina; Sækmose, Susanne Gjørup; Sørensen, Erik; Harritshøj, Lene Holm; Aagaard, Bitten; Dinh, Khoa Manh; Busch, Michael P.; Jørgensen, Charlotte Sværke; Krause, Tyra Grove; Ullum, Henrik; Ostrowski, Sisse Rye; Espenhain, Laura; Pedersen, Ole Birger Vesterager

doi:10.1016/j.lanepe.2022.100479

Cited by 42 publications

(53 citation statements)

References 31 publications

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“…Also, similar to our findings, the scientists showed similar approach has been successfully adopted to rapidly subdue several waves of COVID-19 caused with Omicron BA.2 in China [35,36]. In addition, a large number of established fact proved that effective measures are not taken to respond to Omicron, and the the epidemic will not stop even if the vaccination rate is high [37][38][39], it can cause massive infections, severe infections and many deaths, especially in a country with a large elderly population and a large number of people with chronic illnesses who are at high risk of severe morbidity and mortality [37][38][39]. Hence, adherence to positive control measures can also prevent most people from becoming infected and experiencing long-term COVID-19 symptoms (such as fatigue, breathing difficulties, and cognitive impairment) in the severe patients [40].…”

Section: Discussionsupporting

confidence: 86%

The rapid and efficient strategy for SARS-CoV-2 Omicron transmission control: analysis of outbreaks at the city level

Zheng

Tian

et al. 2022

Infect Dis Poverty

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Background Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron (B.1.1.529) variant is highly transmissible with potential immune escape. Hence, control measures are continuously being optimized to guard against large-scale coronavirus disease 2019 (COVID-19) outbreaks. This study aimed to explore the relationship between the intensity of control measures in response to different SARS-CoV-2 variants and the degree of outbreak control at city level. Methods A retrospective study was conducted in 49 cities with COVID-19 outbreaks between January 2020 and June 2022. Epidemiological data on COVID-19 were extracted from the National Health Commission, People’s Republic of China, and the population flow data were sourced from the Baidu migration data provided by the Baidu platform. Outbreak control was quantified by calculating the degree of infection growth and the time-varying reproduction number ($${R}_{t}$$ R t ). The intensity of the outbreak response was quantified by calculating the reduction in population mobility during the outbreak period. Correlation and regression analyses of the intensity of the control measures and the degree of outbreak control for the Omicron variant and non-Omicron mutants were conducted, respectively. Results Overall, 65 outbreaks occurred in 49 cities in China from January 2020 to June 2022. Of them, 66.2% were Omicron outbreaks and 33.8% were non-Omicron outbreaks. The intensity of the control measures was positively correlated with the degree of outbreak control (r = 0.351, P = 0.03). The degree of reduction in population mobility was negatively correlated with the Rt value (r = − 0.612, P < 0.01). Therefore, under the same control measure intensity, the number of new daily Omicron infections was 6.04 times higher than those attributed to non-Omicron variants, and the Rt value of Omicron outbreaks was 2.6 times higher than that of non-Omicron variants. In addition, the duration of non-Omicron variant outbreaks was shorter than that of the outbreaks caused by the Omicron variant (23.0 ± 10.7, 32.9 ± 16.3, t = 2.243, P = 0.031). Conclusions Greater intensity of control measures was associated with more effective outbreak control. Thus, in response to the Omicron variant, the management to restrict population movement should be used to control its spread quickly, especially in the case of community transmission occurs widely. Faster than is needed for non-Omicron variants, and decisive control measures should be imposed and dynamically adjusted in accordance with the evolving epidemic situation.

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Section: Discussionsupporting

confidence: 86%

The rapid and efficient strategy for SARS-CoV-2 Omicron transmission control: analysis of outbreaks at the city level

Zheng

Tian

et al. 2022

Infect Dis Poverty

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“…Overall ascertainment ratio was 25% (23-27%) from reverse transcription polymerase chain reaction (RT-PCR) testing alone, increasing to 41% (38-45%) if augmented with rapid antigen testing (RAT) ( Figure 2 ). Our Omicron IAR estimates were lower than those reported in South Africa (58% in urban areas)[8], Denmark (66%)[9] and Navarre, Spain (59%)[10], likely reflecting the effectiveness of extensive public health and social measures (PHSMs) imposed in Hong Kong during the fifth wave, such as an universal mask mandate with high community compliance, closure of all bars and limits on opening hours and new ventilation requirements in all restaurants.…”

Section: Main Textcontrasting

confidence: 89%

Population-based sero-epidemiological estimates of real-world vaccine effectiveness against Omicron infection in an infection-naive population, Hong Kong, January to July 2022

Lau

Cheng

Leung

et al. 2022

Preprint

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The SARS-CoV-2 Omicron variant has demonstrated enhanced transmissibility and escape of vaccine-derived immunity. While current vaccines remain effective against severe disease and death, robust evidence on vaccine effectiveness (VE) against all Omicron infections (i.e. irrespective of symptoms) remains sparse. We addressed this knowledge-gap using a community-wide serosurvey with 5,310 subjects by estimating how vaccination histories modulated risk of infection in Hong Kong (which was largely infection naive) during a large wave of Omicron epidemic during January-July 2022. We estimated that Omicron infected 45% (41-48%) of the Hong Kong population. Three and four doses of BNT162b2 or CoronaVac were effective against Omicron infection (VE of 47% (95% credible interval 34-68%) and 70% (43-99%) for three and four doses of BNT162b2 respectively; VE of 31% (1-73%) and 59% (10-99%) for three and four doses of CoronaVac respectively) seven days after vaccination, but protection waned with half-lives of 15 (3-47) weeks for BNT162b2 and 5 (1-37) weeks for CoronaVac. Our findings suggest that booster vaccination can temporarily enhance population immunity ahead of anticipated waves of infections.

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“…While this is extremely well documented from population studies, IFR estimates stratified for comorbidity are typically not available in national seroprevalence studies. A national study of blood donors in Denmark has estimated an IFR of only 0.00336% for people < 51 years without comorbidity, and 0.281% for people aged 61-69 years old without comorbidity (62). The proportion of people with some comorbidities that are very influential for COVID-19 outcomes such as obesity is very different across different countries, even for the same age groups.…”

Section: Discussionmentioning

confidence: 99%

“…During 2021 and 2022, the use of vaccination and the advent of new variants plus pre-existing immunity from prior infections resulted in a marked decline in the IFR. Studies in Denmark (72) and Shanghai (73) (74), suggest that fatality rates may be ten times lower in re-infections versus primary infections. The relative contributions of vaccination, prior infection and new variants in the IFR decline needs careful study and continued monitoring.…”

Section: Discussionmentioning

confidence: 99%

“…During 2021 and 2022, the use of vaccination and the advent of new variants plus pre-existing immunity from prior infections resulted in a marked decline in the IFR. Studies in Denmark (72) and Shanghai (73) suggest that in 2022, IFRs in vaccinated, previously not infected populations were extremely low. For example, in Denmark, IFR was only 1.6 per 100,000 infections for ages 17-35 and even in ages 61-72 it was only 15.1 per 100,000 infections.…”

Section: Discussionmentioning

confidence: 99%

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Age-stratified infection fatality rate of COVID-19 in the non-elderly informed from pre-vaccination national seroprevalence studies

Pezzullo

Axfors

Contopoulos‐Ioannidis

et al. 2022

Preprint

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The infection fatality rate (IFR) of COVID-19 among non-elderly people in the absence of vaccination or prior infection is important to estimate accurately, since 94% of the global population is younger than 70 years and 86% is younger than 60 years. In systematic searches in SeroTracker and PubMed (protocol: https://osf.io/xvupr), we identified 40 eligible national seroprevalence studies covering 38 countries with pre-vaccination seroprevalence data. For 29 countries (24 high-income, 5 others), publicly available age-stratified COVID-19 death data and age-stratified seroprevalence information were available and were included in the primary analysis. The IFRs had a median of 0.035% (interquartile range (IQR) 0.013 - 0.056%) for the 0-59 years old population, and 0.095% (IQR 0.036 - 0.125%,) for the 0-69 years old. The median IFR was 0.0003% at 0-19 years, 0.003% at 20-29 years, 0.011% at 30-39 years, 0.035% at 40-49 years, 0.129% at 50-59 years, and 0.501% at 60-69 years. Including data from another 9 countries with imputed age distribution of COVID-19 deaths yielded median IFR of 0.025-0.032% for 0-59 years and 0.063-0.082% for 0-69 years. Meta-regression analyses also suggested global IFR of 0.03% and 0.07%, respectively in these age groups. The current analysis suggests a much lower pre-vaccination IFR in non-elderly populations than previously suggested. Large differences did exist between countries and may reflect differences in comorbidities and other factors. These estimates provide a baseline from which to fathom further IFR declines with the widespread use of vaccination, prior infections, and evolution of new variants.

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Seroprevalence and infection fatality rate of the SARS-CoV-2 Omicron variant in Denmark: A nationwide serosurveillance study

Cited by 42 publications

References 31 publications

The rapid and efficient strategy for SARS-CoV-2 Omicron transmission control: analysis of outbreaks at the city level

The rapid and efficient strategy for SARS-CoV-2 Omicron transmission control: analysis of outbreaks at the city level

Population-based sero-epidemiological estimates of real-world vaccine effectiveness against Omicron infection in an infection-naive population, Hong Kong, January to July 2022

Age-stratified infection fatality rate of COVID-19 in the non-elderly informed from pre-vaccination national seroprevalence studies

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