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1.
Genome Med ; 14(1): 47, 2022 05 04.
Article in English | MEDLINE | ID: covidwho-1822207

ABSTRACT

BACKGROUND: In early 2021, the SARS-CoV-2 lineage B.1.1.7 (Alpha variant) became dominant across large parts of the world. In Denmark, comprehensive and real-time test, contact-tracing, and sequencing efforts were applied to sustain epidemic control. Here, we use these data to investigate the transmissibility, introduction, and onward transmission of B.1.1.7 in Denmark. METHODS: We analyzed a comprehensive set of 60,178 SARS-CoV-2 genomes generated from high-throughput sequencing by the Danish COVID-19 Genome Consortium, representing 34% of all positive cases in the period 14 November 2020 to 7 February 2021. We calculated the transmissibility of B.1.1.7 relative to other lineages using Poisson regression. Including all 1976 high-quality B.1.1.7 genomes collected in the study period, we constructed a time-scaled phylogeny, which was coupled with detailed travel history and register data to outline the introduction and onward transmission of B.1.1.7 in Denmark. RESULTS: In a period with unchanged restrictions, we estimated an increased B.1.1.7 transmissibility of 58% (95% CI: [56%, 60%]) relative to other lineages. Epidemiological and phylogenetic analyses revealed that 37% of B.1.1.7 cases were related to the initial introduction in November 2020. The relative number of cases directly linked to introductions varied between 10 and 50% throughout the study period. CONCLUSIONS: Our findings corroborate early estimates of increased transmissibility of B.1.1.7. Both substantial early expansion when B.1.1.7 was still unmonitored and continuous foreign introductions contributed considerably to case numbers. Finally, our study highlights the benefit of balanced travel restrictions and self-isolation procedures coupled with comprehensive surveillance efforts, to sustain epidemic control in the face of emerging variants.


Subject(s)
COVID-19 , SARS-CoV-2 , COVID-19/epidemiology , Denmark/epidemiology , Humans , Phylogeny , SARS-CoV-2/genetics
2.
Lancet Infect Dis ; 2022 Apr 22.
Article in English | MEDLINE | ID: covidwho-1799640

ABSTRACT

BACKGROUND: Estimates of the severity of the SARS-CoV-2 omicron variant (B.1.1.529) are crucial to assess the public health impact associated with its rapid global dissemination. We estimated the risk of SARS-CoV-2-related hospitalisations after infection with omicron compared with the delta variant (B.1.617.2) in Denmark, a country with high mRNA vaccination coverage and extensive free-of-charge PCR testing capacity. METHODS: In this observational cohort study, we included all RT-PCR-confirmed cases of SARS-CoV-2 infection in Denmark, with samples taken between Nov 21 (date of first omicron-positive sample) and Dec 19, 2021. Individuals were identified in the national COVID-19 surveillance system database, which included results of a variant-specific RT-PCR that detected omicron cases, and data on SARS-CoV-2-related hospitalisations (primary outcome of the study). We calculated the risk ratio (RR) of hospitalisation after infection with omicron compared with delta, overall and stratified by vaccination status, in a Poisson regression model with robust SEs, adjusted a priori for reinfection status, sex, age, region, comorbidities, and time period. FINDINGS: Between Nov 21 and Dec 19, 2021, among the 188 980 individuals with SARS-CoV-2 infection, 38 669 (20·5%) had the omicron variant. SARS-CoV-2-related hospitalisations and omicron cases increased during the study period. Overall, 124 313 (65·8%) of 188 980 individuals were vaccinated, and vaccination was associated with a lower risk of hospitalisation (adjusted RR 0·24, 95% CI 0·22-0·26) compared with cases with no doses or only one dose of vaccine. Compared with delta infection, omicron infection was associated with an adjusted RR of hospitalisation of 0·64 (95% CI 0·56-0·75; 222 [0·6%] of 38 669 omicron cases admitted to hospital vs 2213 [1·5%] of 150 311 delta cases). For a similar comparison by vaccination status, the RR of hospitalisation was 0·57 (0·44-0·75) among cases with no or only one dose of vaccine, 0·71 (0·60-0·86) among those who received two doses, and 0·50 (0·32-0·76) among those who received three doses. INTERPRETATION: We found a significantly lower risk of hospitalisation with omicron infection compared with delta infection among both vaccinated and unvaccinated individuals, suggesting an inherent reduced severity of omicron. Our results could guide modelling of the effect of the ongoing global omicron wave and thus health-care system preparedness. FUNDING: None.

3.
PLoS One ; 17(3): e0264325, 2022.
Article in English | MEDLINE | ID: covidwho-1714778

ABSTRACT

Patients with severe mental illness (SMI) i.e. schizophrenia, schizoaffective disorder, and bipolar disorder are at increased risk of severe outcomes if infected with coronavirus disease 2019 (COVID-19). Whether patients with SMI are at increased risk of COVID-19 is, however, sparsely investigated. This important issue must be addressed as the current pandemic could have the potential to increase the existing gap in lifetime mortality between this group of patients and the background population. The objective of this study was to determine whether a diagnosis of schizophrenia, schizoaffective disorder, or bipolar disorder is associated with an increased risk of COVID-19. A cross-sectional study was performed between January 18th and February 25th, 2021. Of 7071 eligible patients with schizophrenia, schizoaffective disorder, or bipolar disorder, 1355 patients from seven psychiatric centres in the Capital Region of Denmark were screened for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies. A total of 1258 unvaccinated patients were included in the analysis. The mean age was 40.5 years (SD 14.6), 54.3% were female. Fifty-nine of the 1258 participants had a positive SARS-CoV-2 antibody test, corresponding to a adjusted seroprevalence of 4.96% (95% CI 3.87-6.35). No significant difference in SARS-CoV-2-risk was found between female and male participants (RR = 1.32; 95% CI 0.79-2.20; p = .290). No significant differences in seroprevalences between schizophrenia and bipolar disease were found (RR = 1.12; 95% CI 0.67-1.87; p = .667). Seroprevalence among 6088 unvaccinated blood donors from the same region and period was 12.24% (95% CI 11.41-13.11). SARS-CoV-2 seroprevalence among included patients with SMI was significantly lower than among blood donors (RR = 0.41; 95% CI 0.31-0.52; p < .001). Differences in seroprevalences remained significant when adjusting for gender and age, except for those aged 60 years or above. The study is registered at ClinicalTrails.gov (NCT04775407). https://clinicaltrials.gov/ct2/show/NCT04775407?term=NCT04775407&draw=2&rank=1.


Subject(s)
Antibodies, Viral/blood , COVID-19 , Mental Disorders , SARS-CoV-2/metabolism , Adult , COVID-19/blood , COVID-19/epidemiology , Cross-Sectional Studies , Female , Humans , Male , Mental Disorders/blood , Mental Disorders/epidemiology , Middle Aged , Seroepidemiologic Studies
4.
BMC Infect Dis ; 22(1): 143, 2022 Feb 10.
Article in English | MEDLINE | ID: covidwho-1690954

ABSTRACT

BACKGROUND: COVID-19 is thought to be more prevalent among ethnic minorities and individuals with low socioeconomic status. We aimed to investigate the prevalence of SARS-CoV-2 antibodies during the COVID-19 pandemic among citizens 15 years or older in Denmark living in social housing (SH) areas. METHODS: We conducted a study between January 8th and January 31st, 2021 with recruitment in 13 selected SH areas. Participants were offered a point-of-care rapid SARS-CoV-2 IgM and IgG antibody test and a questionnaire concerning risk factors associated with COVID-19. As a proxy for the general Danish population we accessed data on seroprevalence from Danish blood donors (total Ig ELISA assay) in same time period. RESULTS: Of the 13,279 included participants, 2296 (17.3%) were seropositive (mean age 46.6 (SD 16.4) years, 54.2% female), which was 3 times higher than in the general Danish population (mean age 41.7 (SD 14.1) years, 48.5% female) in the same period (5.8%, risk ratios (RR) 2.96, 95% CI 2.78-3.16, p > 0.001). Seropositivity was higher among males (RR 1.1, 95% CI 1.05-1.22%, p = 0.001) and increased with age, with an OR seropositivity of 1.03 for each 10-year increase in age (95% CI 1.00-1.06, p = 0.031). Close contact with COVID-19-infected individuals was associated with a higher risk of infection, especially among household members (OR 5.0, 95% CI 4.1-6.2 p < 0,001). Living at least four people in a household significantly increased the OR of seropositivity (OR 1.3, 95% CI 1.0-1.6, p = 0.02) as did living in a multi-generational household (OR 1.3 per generation, 95% CI 1.1-1.6, p = 0.003). Only 1.6% of participants reported not following any of the national COVID-19 recommendations. CONCLUSIONS: Danish citizens living in SH areas of low socioeconomic status had a three times higher SARS-CoV-2 seroprevalence compared to the general Danish population. The seroprevalence was significantly higher in males and increased slightly with age. Living in multiple generations households or in households of more than four persons was a strong risk factor for being seropositive. Results of this study can be used for future consideration of the need for preventive measures in the populations living in SH areas.


Subject(s)
COVID-19 , SARS-CoV-2 , Adult , Antibodies, Viral , Denmark/epidemiology , Female , Housing , Humans , Male , Middle Aged , Pandemics , Seroepidemiologic Studies
5.
EuropePMC;
Preprint in English | EuropePMC | ID: ppcovidwho-327773

ABSTRACT

The newly found Omicron SARS-CoV-2 variant of concern has rapidly spread worldwide. Omicron carries numerous mutations in key regions and is associated with increased transmissibility and immune escape. The variant has recently been divided into four subvariants with substantial genomic differences, in particular between Omicron BA.1 and BA.2. With the surge of Omicron subvariants BA.1 and BA.2, a large number of reinfections from earlier cases has been observed, raising the question of whether BA.2 specifically can escape the natural immunity acquired shortly after a BA.1 infection. To investigate this, we selected a subset of samples from more than 1,8 million cases of infections in the period from November 22, 2021, until February 11, 2022. Here, individuals with two positive samples, more than 20 and less than 60 days apart, were selected. From a total of 187 reinfection cases, we identified 47 instances of BA.2 reinfections shortly after a BA.1 infection, mostly in young unvaccinated individuals with mild disease not resulting in hospitalization or death. In conclusion, we provide evidence that Omicron BA.2 reinfections do occur shortly after BA.1 infections but are rare.

6.
EuropePMC;
Preprint in English | EuropePMC | ID: ppcovidwho-327249

ABSTRACT

1 The Omicron SARS-CoV-2 variant of concern (VOC lineage B.1.1.529), which became dominant in many countries during early 2022, includes several subvariants with strikingly different genetic characteristics. Several countries, including Denmark, have observed the two Omicron subvariants: BA.1 and BA.2. In Denmark the latter has rapidly replaced the former as the dominant subvariant. Based on nationwide Danish data, we estimate the transmission dynamics of BA.1 and BA.2 following the spread of Omicron VOC within Danish households in late December 2021 and early January 2022. Among 8,541 primary household cases, of which 2,122 were BA.2, we identified a total of 5,702 secondary infections among 17,945 potential secondary cases during a 1-7 day follow-up period. The secondary attack rate (SAR) was estimated as 29% and 39% in households infected with Omicron BA.1 and BA.2, respectively. We found BA.2 to be associated with an increased susceptibility of infection for unvaccinated individuals (Odds Ratio (OR) 2.19;95%-CI 1.58-3.04), fully vaccinated individuals (OR 2.45;95%-CI 1.77-3.40) and booster-vaccinated individuals (OR 2.99;95%-CI 2.11-4.24), compared to BA.1. We also found an increased transmissibility from unvaccinated primary cases in BA.2 households when compared to BA.1 households, with an OR of 2.62 (95%-CI 1.96-3.52). The pattern of increased transmissibility in BA.2 households was not observed for fully vaccinated and booster-vaccinated primary cases, where the OR of transmission was below 1 for BA.2 compared to BA.1. We conclude that Omicron BA.2 is inherently substantially more transmissible than BA.1, and that it also possesses immune-evasive properties that further reduce the protective effect of vaccination against infection, but do not increase its transmissibility from vaccinated individuals with breakthrough infections.

7.
Euro Surveill ; 27(6)2022 02.
Article in English | MEDLINE | ID: covidwho-1686389

ABSTRACT

BackgroundThe 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.AimThe objective of this observational study was to investigate SARS-CoV-2 transmission in Danish households during the early stages of the COVID-19 pandemic.MethodsWe 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.ResultsWe 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).ConclusionsAlthough 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.


Subject(s)
COVID-19 , SARS-CoV-2 , Adolescent , Adult , Child , Denmark/epidemiology , Humans , Infection Control , Pandemics
8.
Microbiol Spectr ; 9(3): e0133021, 2021 12 22.
Article in English | MEDLINE | ID: covidwho-1583201

ABSTRACT

"Testing Denmark" is a national, large-scale, epidemiological surveillance study of SARS-CoV-2 in the Danish population. Between September and October 2020, approximately 1.3 million people (age >15 years) were randomly invited to fill in an electronic questionnaire covering COVID-19 exposures and symptoms. The prevalence of SARS-CoV-2 antibodies was determined by point-of care rapid test (POCT) distributed to participants' home addresses. In total, 318,552 participants (24.5% invitees) completed the study and 2,519 (0.79%) were seropositive. Of the participants with a prior positive PCR test (n = 1,828), 29.1% were seropositive in the POCT. Although seropositivity increased with age, participants 61 years and over reported fewer symptoms and were tested less frequently. Seropositivity was associated with physical contact with SARS-CoV-2 infected individuals (risk ratio [RR] 7.43, 95% CI: 6.57-8.41), particular in household members (RR 17.70, 95% CI: 15.60-20.10). A greater risk of seropositivity was seen in home care workers (RR 2.09, 95% CI: 1.58-2.78) compared to office workers. A high degree of adherence with national preventive recommendations was reported (e.g., >80% use of face masks), but no difference were found between seropositive and seronegative participants. The seroprevalence result was somewhat hampered by a lower-than-expected performance of the POCT. This is likely due to a low sensitivity of the POCT or problems reading the test results, and the main findings therefore relate to risk associations. More emphasis should be placed on age, occupation, and exposure in local communities. IMPORTANCE To date, including 318,522 participants, this is the largest population-based study with broad national participation where tests and questionnaires have been sent to participants' homes. We found that more emphasis from national and local authorities toward the risk of infection should be placed on age of tested individuals, type of occupation, as well as exposure in local communities and households. To meet the challenge that broad nationwide information can be difficult to gather. This study design sets the stage for a novel way of conducting studies. Additionally, this study design can be used as a supplementary model in future general test strategy for ongoing monitoring of COVID-19 immunity in the population, both from past infection and from vaccination against SARS-CoV-2, however, with attention to the complexity of performing and reading the POCT at home.


Subject(s)
COVID-19/diagnosis , COVID-19/epidemiology , SARS-CoV-2 , Adult , Antibodies, Viral , COVID-19/immunology , Denmark , Female , Humans , Immunity , Immunoglobulin G/blood , Immunoglobulin M/blood , Male , Middle Aged , Odds Ratio , Point-of-Care Testing , Population Surveillance , Prevalence , SARS-CoV-2/isolation & purification , Seroepidemiologic Studies , Surveys and Questionnaires
9.
Nat Commun ; 12(1): 7251, 2021 12 13.
Article in English | MEDLINE | ID: covidwho-1569250

ABSTRACT

New lineages of SARS-CoV-2 are of potential concern due to higher transmissibility, risk of severe outcomes, and/or escape from neutralizing antibodies. Lineage B.1.1.7 (the Alpha variant) became dominant in early 2021, but the association between transmissibility and risk factors, such as age of primary case and viral load remains poorly understood. Here, we used comprehensive administrative data from Denmark, comprising the full population (January 11 to February 7, 2021), to estimate household transmissibility. This study included 5,241 households with primary cases; 808 were infected with lineage B.1.1.7 and 4,433 with other lineages. Here, we report an attack rate of 38% in households with a primary case infected with B.1.1.7 and 27% in households with other lineages. Primary cases infected with B.1.1.7 had an increased transmissibility of 1.5-1.7 times that of primary cases infected with other lineages. The increased transmissibility of B.1.1.7 was multiplicative across age and viral load.


Subject(s)
Age Factors , COVID-19/transmission , SARS-CoV-2 , Viral Load , Adolescent , Adult , Aged , Aged, 80 and over , COVID-19/epidemiology , Child , Child, Preschool , Denmark/epidemiology , Female , Humans , Infant , Infant, Newborn , Male , Middle Aged , Young Adult
10.
2021.
Preprint in English | Other preprints | ID: ppcovidwho-295360

ABSTRACT

Aim The objective of this nationwide study was to investigate the association between SARS-CoV-2 transmissibility, viral load, and age of primary cases in Danish households. Background Spread in households represents a major mode of transmission of SARS-CoV-2. In order to take proper action against the spread of the disease, it is important to have a better understanding of transmission in the household domain—including the role of viral load of primary cases. Methods The study was designed as an observational cohort study, using detailed administrative register data. We included the full population of Denmark and all SARS-CoV-2 tests (August 25, 2020 to February 10, 2021) to estimate transmissibility in house-holds comprising 2-6 people. RT-PCR Cycle threshold (Ct) values were used as a proxy for viral load. Results We identified 63,657 primary cases and 139,882 household members of which 21% tested positive by RT-PCR within a 1-14 day period after the primary case. There was an approximately linear association between Ct value of the sample and transmissibility, implying that cases with samples having a higher viral load were more transmissible than cases with samples having a lower viral load. However, even for primary cases with relatively high sample Ct values, the transmissibility was not negligible, e.g., for primary cases with a sample Ct value of 38, we found that 13% of the primary cases had at least one secondary household case. Moreover, 34% of all secondary cases were found in households with primary cases having sample Ct values >30. An increasing transmissibility with age of the primary cases for adults (≥20 years) and a decreasing transmissibility with age for children (<20 years) were found. Conclusions Although primary cases with sample high viral loads (low Ct values) were associated with higher SARS-CoV-2 transmissibility, we found no obvious cut-off for sample Ct values to eliminate transmissibility and a substantial amount of household transmission occurred in households where the primary cases had high sample Ct values (low viral load), The study further showed that transmissibility increases with age. These results have important public health implications, as they suggest that contact tracing should prioritize cases according to Ct values and age, and underline the importance of quick identification and isolation of cases. Furthermore, the study highlights that households can serve as a transmission bridge by creating connections between otherwise separate domains.

11.
Clin Infect Dis ; 73(9): e2962-e2969, 2021 11 02.
Article in English | MEDLINE | ID: covidwho-1501026

ABSTRACT

BACKGROUND: Although the vast majority of individuals succumbing to infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are elderly, infection fatality rate (IFR) estimates for the age group ≥70 years are still scarce. To this end, we assessed SARS-CoV-2 seroprevalence among retired blood donors and combined it with national coronavirus disease 2019 (COVID-19) survey data to provide reliable population-based IFR estimates for this age group. METHODS: We identified 60 926 retired blood donors aged ≥70 years in the rosters of 3 regionwide Danish blood banks and invited them to fill in a questionnaire on COVID-19-related symptoms and behaviors. Among 24 861 (40.8%) responders, we invited a random sample of 3200 individuals for blood testing. Overall, 1201 (37.5%) individuals were tested for SARS-CoV-2 antibodies (Wantai) and compared with 1110 active blood donors aged 17-69 years. Seroprevalence 95% confidence intervals (CIs) were adjusted for assay sensitivity and specificity. RESULTS: Among retired (aged ≥70 years) and active (aged 17-69 years) blood donors, adjusted seroprevalences were 1.4% (95% CI, .3-2.5%) and 2.5% (95% CI, 1.3-3.8%), respectively. Using available population data on COVID-19-related fatalities, IFRs for patients aged ≥70 years and for 17-69 years were estimated at 5.4% (95% CI, 2.7-6.4%) and .083% (95% CI, .054-.18%), respectively. Only 52.4% of SARS-CoV-2-seropositive retired blood donors reported having been sick since the start of the pandemic. CONCLUSIONS: COVID-19 IFR in the age group >69 years is estimated to be 65 times the IFR for people aged 18-69 years.


Subject(s)
COVID-19 , SARS-CoV-2 , Aged , Antibodies, Viral , Blood Donors , Cross-Sectional Studies , Denmark , Humans , Seroepidemiologic Studies
12.
Lancet Infect Dis ; 21(11): 1507-1517, 2021 11.
Article in English | MEDLINE | ID: covidwho-1492844

ABSTRACT

BACKGROUND: The more infectious SARS-CoV-2 lineage B.1.1.7 rapidly spread in Europe after December, 2020, and a concern that B.1.1.7 could cause more severe disease has been raised. Taking advantage of Denmark's high RT-PCR testing and whole genome sequencing capacities, we used national health register data to assess the risk of COVID-19 hospitalisation in individuals infected with B.1.1.7 compared with those with other SARS-CoV-2 lineages. METHODS: We did an observational cohort study of all SARS-CoV-2-positive cases confirmed by RT-PCR in Denmark, sampled between Jan 1 and March 24, 2021, with 14 days of follow-up for COVID-19 hospitalisation. Cases were identified in the national COVID-19 surveillance system database, which includes data from the Danish Microbiology Database (RT-PCR test results), the Danish COVID-19 Genome Consortium, the National Patient Registry, the Civil Registration System, as well as other nationwide registers. Among all cases, COVID-19 hospitalisation was defined as first admission lasting longer than 12 h within 14 days of a sample with a positive RT-PCR result. The study population and main analysis were restricted to the proportion of cases with viral genome data. We calculated the risk ratio (RR) of admission according to infection with B.1.1.7 versus other co-existing lineages with a Poisson regression model with robust SEs, adjusted a priori for sex, age, calendar time, region, and comorbidities. The contribution of each covariate to confounding of the crude RR was evaluated afterwards by a stepwise forward inclusion. FINDINGS: Between Jan 1 and March 24, 2021, 50 958 individuals with a positive SARS-CoV-2 test and at least 14 days of follow-up for hospitalisation were identified; 30 572 (60·0%) had genome data, of whom 10 544 (34·5%) were infected with B.1.1.7. 1944 (6·4%) individuals had a COVID-19 hospitalisation and of these, 571 (29·4%) had a B.1.1.7 infection and 1373 (70·6%) had an infection with other SARS-CoV-2 lineages. Although the overall number of hospitalisations decreased during the study period, the proportion of individuals infected with B.1.1.7 increased from 3·5% to 92·1% per week. B.1.1.7 was associated with a crude RR of hospital admission of 0·79 (95% CI 0·72-0·87; p<0·0001) and an adjusted RR of 1·42 (95% CI 1·25-1·60; p<0·0001). The adjusted RR was increased in all strata of age and calendar period-the two covariates with the largest contribution to confounding of the crude RR. INTERPRETATION: Infection with SARS-CoV-2 lineage B.1.1.7 was associated with an increased risk of hospitalisation compared with that of other lineages in an analysis adjusted for covariates. The overall effect on hospitalisations in Denmark was lessened due to a strict lockdown, but our findings could support hospital preparedness and modelling of the projected impact of the epidemic in countries with uncontrolled spread of B.1.1.7. FUNDING: None.


Subject(s)
COVID-19/epidemiology , Hospitalization/statistics & numerical data , SARS-CoV-2/isolation & purification , Adolescent , Adult , COVID-19/diagnosis , COVID-19/therapy , COVID-19/transmission , COVID-19 Nucleic Acid Testing/statistics & numerical data , Child , Child, Preschool , Cohort Studies , Comorbidity , Denmark/epidemiology , Female , Genome, Viral/genetics , Humans , Infant , Infant, Newborn , Male , Middle Aged , RNA, Viral/genetics , RNA, Viral/isolation & purification , Risk Assessment/statistics & numerical data , SARS-CoV-2/genetics , SARS-CoV-2/pathogenicity , Whole Genome Sequencing/statistics & numerical data , Young Adult
14.
Clin Infect Dis ; 73(9): e2962-e2969, 2021 11 02.
Article in English | MEDLINE | ID: covidwho-889496

ABSTRACT

BACKGROUND: Although the vast majority of individuals succumbing to infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are elderly, infection fatality rate (IFR) estimates for the age group ≥70 years are still scarce. To this end, we assessed SARS-CoV-2 seroprevalence among retired blood donors and combined it with national coronavirus disease 2019 (COVID-19) survey data to provide reliable population-based IFR estimates for this age group. METHODS: We identified 60 926 retired blood donors aged ≥70 years in the rosters of 3 regionwide Danish blood banks and invited them to fill in a questionnaire on COVID-19-related symptoms and behaviors. Among 24 861 (40.8%) responders, we invited a random sample of 3200 individuals for blood testing. Overall, 1201 (37.5%) individuals were tested for SARS-CoV-2 antibodies (Wantai) and compared with 1110 active blood donors aged 17-69 years. Seroprevalence 95% confidence intervals (CIs) were adjusted for assay sensitivity and specificity. RESULTS: Among retired (aged ≥70 years) and active (aged 17-69 years) blood donors, adjusted seroprevalences were 1.4% (95% CI, .3-2.5%) and 2.5% (95% CI, 1.3-3.8%), respectively. Using available population data on COVID-19-related fatalities, IFRs for patients aged ≥70 years and for 17-69 years were estimated at 5.4% (95% CI, 2.7-6.4%) and .083% (95% CI, .054-.18%), respectively. Only 52.4% of SARS-CoV-2-seropositive retired blood donors reported having been sick since the start of the pandemic. CONCLUSIONS: COVID-19 IFR in the age group >69 years is estimated to be 65 times the IFR for people aged 18-69 years.


Subject(s)
COVID-19 , SARS-CoV-2 , Aged , Antibodies, Viral , Blood Donors , Cross-Sectional Studies , Denmark , Humans , Seroepidemiologic Studies
15.
Clin Infect Dis ; 72(2): 249-253, 2021 01 27.
Article in English | MEDLINE | ID: covidwho-614253

ABSTRACT

BACKGROUND: The pandemic due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has tremendous consequences for our societies. Knowledge of the seroprevalence of SARS-CoV-2 is needed to accurately monitor the spread of the epidemic and to calculate the infection fatality rate (IFR). These measures may help the authorities make informed decisions and adjust the current societal interventions. The objective was to perform nationwide real-time seroprevalence surveying among blood donors as a tool to estimate previous SARS-CoV-2 infections and the population-based IFR. METHODS: Danish blood donors aged 17-69 years giving blood 6 April to 3 May were tested for SARS-CoV-2 immunoglobulin M and G antibodies using a commercial lateral flow test. Antibody status was compared between geographical areas, and an estimate of the IFR was calculated. Seroprevalence was adjusted for assay sensitivity and specificity taking the uncertainties of the test validation into account when reporting the 95% confidence intervals (CIs). RESULTS: The first 20 640 blood donors were tested, and a combined adjusted seroprevalence of 1.9% (95% CI, .8-2.3) was calculated. The seroprevalence differed across areas. Using available data on fatalities and population numbers, a combined IFR in patients <70 years is estimated at 89 per 100 000 (95% CI, 72-211) infections. CONCLUSIONS: The IFR was estimated to be slightly lower than previously reported from other countries not using seroprevalence data. The IFR is likely severalfold lower than the current estimate. We have initiated real-time nationwide anti-SARS-CoV-2 seroprevalence surveying of blood donations as a tool in monitoring the epidemic.


Subject(s)
Blood Donors , COVID-19 , Adolescent , Adult , Aged , Antibodies, Viral , Humans , Middle Aged , SARS-CoV-2 , Seroepidemiologic Studies , Young Adult
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