Factors associated with the formation of SARS-CoV-2 case-clusters in Danish schools: a nationwide register-based observational study

A register-based retrospective observational study was conducted to describe SARS-CoV-2 cases and case-clusters in schoolchildren of Danish primary and lower secondary schools and identify which factors were associated with the occurrence of case-clusters in schools. The study period was the autumn school semester 2021. Clusters were defined as three or more cases in a school-class level within 14 days. Descriptive analysis was carried out and multivariable logistic regression analysis was performed to determine which factors were associated with case introductions (i.e., primary case) being linked to a cluster. More cases and clusters were identified in lower than in higher class levels. Out of 21,497 cases introduced into a school, 41.6% started a cluster. A higher assumed immunity level in a class level was significantly reducing the odds of a case introduction being linked to a cluster (e.g., assumed immunity of ≥80% vs <20%: OR: 0.28; 95%CI: 0.17-0.44). A previous infection (in the primary case) had a protective effect (OR: 0.58; 95%CI: 0.33-0.99). This study suggests that most cases appearing in schools did not induce clusters, but that once cluster occur sizes can be large. It further indicates that vaccination of children markedly reduces the risk of secondary infections.

Large Multicountry Outbreak of Invasive Listeriosis by a Listeria monocytogenes ST394 Clone Linked to Smoked Rainbow Trout, 2020 to 2021

Whole-genome sequencing (WGS) has revolutionized surveillance of infectious diseases. Disease outbreaks can now be detected with high precision, and correct attribution of infection sources has been improved. Listeriosis, caused by the bacterium Listeria monocytogenes, is a foodborne disease with a high case fatality rate and a large proportion of outbreak-related cases. Timely recognition of listeriosis outbreaks and precise allocation of food sources are important to prevent further infections and to promote public health. We report the WGS-based identification of a large multinational listeriosis outbreak with 55 cases that affected Germany, Austria, Denmark, and Switzerland during 2020 and 2021. Clinical isolates formed a highly clonal cluster (called Ny9) based on core genome multilocus sequence typing (cgMLST). Routine and ad hoc investigations of food samples identified L. monocytogenes isolates from smoked rainbow trout filets from a Danish producer grouping with the Ny9 cluster. Patient interviews confirmed consumption of rainbow trout as the most likely infection source. The Ny9 cluster was caused by a MLST sequence type (ST) ST394 clone belonging to molecular serogroup IIa, forming a distinct clade within molecular serogroup IIa strains. Analysis of the Ny9 genome revealed clpY, dgcB, and recQ inactivating mutations, but phenotypic characterization of several virulence-associated traits of a representative Ny9 isolate showed that the outbreak strain had the same pathogenic potential as other serogroup IIa strains. Our report demonstrates that international food trade can cause multicountry outbreaks that necessitate cross-border outbreak collaboration. It also corroborates the relevance of ready-to-eat smoked fish products as causes for listeriosis. IMPORTANCE Listeriosis is a severe infectious disease in humans and characterized by an exceptionally high case fatality rate. The disease is transmitted through consumption of food contaminated by the bacterium Listeria monocytogenes. Outbreaks of listeriosis often occur but can be recognized and stopped through implementation of whole-genome sequencing-based pathogen surveillance systems. We here describe the detection and management of a large listeriosis outbreak in Germany and three neighboring countries. This outbreak was caused by rainbow trout filet, which was contaminated by a L. monocytogenes clone belonging to sequence type ST394. This work further expands our knowledge on the genetic diversity and transmission routes of an important foodborne pathogen.

Findings in Danish long-term care facilities in the first year of the SARS-CoV-2 pandemic

PURPOSE

To describe the occurrence of SARS-CoV-2 infections, deaths and outbreaks among residents in Danish long-term care facilities (LTCFs) from February 2020 to February 2021.

METHODS

Danish COVID-19 national register data from a newly implemented automated surveillance system was used to describe incidence rate and deaths (per 1000 residents' years), number of tests, SARS-CoV-2 infections and outbreaks among LTCF residents. A case was defined as a LTCF resident with a positive SARS-CoV-2 PCR test. An outbreak was defined as two or more cases in one LTCF within a 14-day period, and considered closed if no new cases had occurred within 28 days. Death was defined as occurring within 30-days of a positive test.

RESULTS

A total of 55,359 residents living in 948 LTCFs were included. The median age of the residents was 85 years and 63% were female. There was a total of 3712 cases found among residents across 43% of all LTCFs. Nearly all (94%) cases were linked to outbreaks. Higher numbers of cases and outbreaks were seen in Denmark's Capital Region compared to other regions. Overall, 22 SARS-CoV-2 deaths and 359 deaths (non-SARS-CoV-2) per 1000 resident years were identified in the study period.

CONCLUSION

Less than half of LTCFs identified any cases. The majority of cases were linked to outbreaks, emphasizing the importance of preventing introductions of SARS-CoV-2 into the facilities. Furthermore, it highlights the need to invest efforts into infrastructures, routine procedures and monitoring of SARS-CoV-2 in LTCFs to limit the introduction and the spread of SARS-CoV-2.

Seroprevalence of SARS-CoV-2 Antibodies in Denmark: Results of Two Nationwide Population-Based Surveys, February and May 2021

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.

When schools were open for in-person teaching during the COVID-19 pandemic - the nordic experience on control measures and transmission in schools during the delta wave

BACKGROUND

Extensive measures to control spread of SARS-CoV-2 have led to limited access to education for millions of children and adolescents during the COVID-19 pandemic. Education and access to schools is vital for children and adolescents' learning, health, and wellbeing. Based on high vaccine uptake and low incidence levels, the Nordic countries (Denmark, Finland, Iceland, Norway and Sweden) decided to start the academic year 2021/22 with schools open for in-person teaching and moderate mitigation measures. We describe trends in SARS-CoV-2 infections and vaccination coverage among students during the first 12 weeks of the fall semester.

METHODS

In this multinational, retrospective, observational study, we have used surveillance and registry data from each of the Nordic countries to describe vaccine uptake (≥12 years), infection incidence (whole population) and transmission of SARS-CoV-2 among students. The study period, week 30 to 41 (Jul 26th - Oct 17th), represents the autumn semester from immediately before school started until fall break. In addition, we collected information on mitigation measures applied by the respective countries.

RESULTS

There were slight variations between the countries regarding existing infection prevention and control (IPC) measures, testing strategies and vaccination start-up among adolescents. All countries had high vaccine uptake in the adult population, while uptake varied more in the younger age groups. Incidence in the school-aged population differed between countries and seemed to be influenced by both vaccine uptake and test activity. Infection clusters among school-aged children were described for Denmark and Norway, and the number of clusters per week reflected the incidence trend of the country. Most events consisted of only 1-2 cases. Larger clusters appeared more frequently in the higher grades in Norway and in lower grades in Denmark.

CONCLUSION

Data from the Nordic countries indicate that vaccination of adults and adolescents, in addition to mitigation measures, enabled full in-person learning. As SARS-CoV-2 infection does not represent a severe medical risk for most children as previously thought, measures targeting this group should be carefully adjusted and kept at a minimum. Our data add to the evidence on incidence and transmission of SARS-CoV-2 among students in schools open for in-person teaching, and may be valuable for decision makers worldwide.

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

Background

Introduction of the Omicron variant caused a steep rise in SARS-CoV-2 infections despite high vaccination coverage in the Danish population. We used blood donor serosurveillance to estimate the percentage of recently infected residents in the similarly aged background population with no known comorbidity.

Methods

To detect SARS-CoV-2 antibodies induced due to recent infection, and not vaccination, we assessed anti-nucleocapsid (anti-N) immunoglobulin G (IgG) in blood donor samples. Individual level data on SARS-CoV-2 RT-PCR results and vaccination status were available. Anti-N IgG was measured fortnightly from January 18 to April 3, 2022. Samples from November 2021 were analysed to assess seroprevalence before introduction of the Omicron variant in Denmark.

Findings

A total of 43 088 donations from 35 309 Danish blood donors aged 17–72 years were screened. In November 2021, 1·2% (103/8 701) of donors had detectable anti-N IgG antibodies. Adjusting for test sensitivity (estimates ranging from 74%–81%) and November seroprevalence, we estimate that 66% (95% confidence intervals (CI): 63%–70%) of the healthy, similarly aged Danish population had been infected between November 1, 2021, and March 15, 2022. One third of infections were not captured by SARS-CoV-2 RT-PCR testing. The infection fatality rate (IFR) was 6·2 (CI: 5·1–7·5) per 100 000 infections.

Interpretation

Screening for anti-N IgG and linkage to national registers allowed us to detect recent infections and accurately assess assay sensitivity in vaccinated or previously infected individuals during the Omicron outbreak. The IFR was lower than during previous waves.

Funding

The Danish Ministry of Health.

Risk and Phenotype of Multisystem Inflammatory Syndrome in Vaccinated and Unvaccinated Danish Children Before and During the Omicron Wave

This cohort study investigates the risk of multisystem inflammatory syndrome after SARS-CoV-2 infection in vaccinated and unvaccinated children before and during the Omicron wave in Denmark.

Disability adjusted life years associated with COVID-19 in Denmark in the first year of the pandemic

Background

Burden of disease studies measure the public health impact of a disease in a society. The aim of this study was to quantify the direct burden of COVID-19 in the first 12 months of the epidemic in Denmark.

Methods

We collected national surveillance data on positive individuals for SARS-CoV-2 with RT-PCR, hospitalization data, and COVID-19 mortality reported in the period between 26^th of February, 2020 to 25^th of February, 2021. We calculated disability adjusted life years (DALYs) based on the European Burden of Disease Network consensus COVID-19 model, which considers mild, severe, critical health states, and premature death. We conducted sensitivity analyses for two different death-registration scenarios, within 30 and 60 days after first positive test, respectively.

Results

We estimated that of the 211,823 individuals who tested positive to SARS-CoV-2 by RT-PCR in the one-year period, 124,163 (59%; 95% uncertainty interval (UI) 112,782–133,857) had at least mild symptoms of disease. The total estimated disease burden was 30,180 DALYs (95% UI 30,126; 30,242), corresponding to 520 DALYs/100,000. The disease burden was higher in the age groups above 70 years of age, particularly in men. Years of life lost (YLL) contributed with more than 99% of total DALYs. The results of the scenario analysis showed that defining COVID-19-related fatalities as deaths registered up to 30 days after the first positive test led to a lower YLL estimate than when using a 60-days window.

Conclusion

COVID-19 led to a substantial public health impact in Denmark in the first full year of the epidemic. Our estimates suggest that it was the the sixth most frequent cause of YLL in Denmark in 2020. This impact will be higher when including the post-acute consequences of COVID-19 and indirect health outcomes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-13694-9.

[COVID-19 among children and adolescents]

Children and adolescents infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are usually asymptomatic or have mild coronavirus disease (COVID-19) with low rates of hospitalization and death. Multisystem inflammatory syndrome in children (MIS-C) is a rare and severe complication of SARS-CoV-2 infection. This paper reviews an excerpt of the literature on disease burden and complications following COVID-19 in children and adolescents aged 0-17 years, in addition to the effects and adverse drug reactions of BNT162b2 and mRNA-1273 vaccinations among children and adolescents aged 5-17 years.

Case-control study of activities associated with SARS-CoV-2 infection in an adult unvaccinated population and overview of societal COVID-19 epidemic counter measures in Denmark

Measures to restrict physical inter-personal contact in the community have been widely implemented during the COVID-19 pandemic. We studied determinants for infection with SARS-CoV-2 with the aim of informing future public health measures. We conducted a national matched case-control study among unvaccinated not previously infected adults aged 18-49 years. Cases were selected among those testing positive for SARS-CoV-2 by RT-PCR over a five-day period in June 2021. Controls were selected from the national population register and were individually matched on age, sex and municipality of residence. Cases and controls were interviewed via telephone about contact with other persons and exposures in the community. We determined matched odds ratios (mORs) and 95% confidence intervals (95%CIs) by conditional logistical regression with adjustment for household size and immigration status. For reference, we provide a timeline of non-pharmaceutical interventions in place in Denmark from February 2020 to March 2022. We included 500 cases and 529 controls. We found that having had contact with another individual with a known infection was the main determinant for SARS-CoV-2 infection: reporting close contact with an infected person who either had or did not have symptoms resulted in mORs of 20 (95%CI:9.8-39) and 8.5 (95%CI 4.5-16) respectively. Community exposures were generally not associated with disease; several exposures were negatively associated. Consumption of alcohol in restaurants or cafés, aOR = 2.3 (95%CI:1.3-4.2) and possibly attending fitness centers, mOR = 1.4 (95%CI:1.0-2.0) were weakly associated with SARS-CoV-2 infection. Apart from these two factors, no community activities were more common amongst cases under the community restrictions in place during the study. The strongest risk factor for transmission was contact to an infected person. Results were in agreement with findings of our similar study conducted six month earlier.

Epidemiological characterisation of the first 785 SARS-CoV-2 Omicron variant cases in Denmark, December 2021

By 9 December 2021, 785 SARS-CoV-2 Omicron variant cases have been identified in Denmark. Most cases were fully (76%) or booster-vaccinated (7.1%); 34 (4.3%) had a previous SARS-CoV-2 infection. The majority of cases with available information reported symptoms (509/666; 76%) and most were infected in Denmark (588/644; 91%). One in five cases cannot be linked to previous cases, indicating widespread community transmission. Nine cases have been hospitalised, one required intensive care and no deaths have been registered.

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.

Prevalence of SARS-CoV-2 antibodies in Denmark: nationwide, population-based seroepidemiological study

Seroprevalence studies have proven an important tool to monitor the progression of the coronavirus disease 2019 (COVID-19) pandemic. We present results of consecutive population-based seroprevalence surveys performed in Denmark in 2020. In spring, late summer and autumn/winter of 2020, invitation letters including a questionnaire covering symptoms were sent to representative samples of the population above 12 years and to parents of children below 18 years in the sample. Blood samples were analysed for total Ig and seroprevalence estimates per population segment were calculated and compared to other surveillance parameters. Based on 34 081 participants (participation rate 33%), seroprevalence estimates increased from 1.2% (95%CI: 0.3-1.9%) in May to 4.1% (95%CI: 3.1-4.9%) in December 2020. Seroprevalence estimates were roughly three times higher in those aged 12-29 years compared to 65 + and higher in metropolitan municipalities. By December 2020, 1.5% of the population had tested positive by RT-PCR. Infected individuals in older age groups were hospitalised several fold more often than in younger. Amongst seropositives, loss of taste/smell were the more specific symptoms, 32-56% did not report any symptoms. In more than half of seroconverted families, we did not see evidence of transmission between generations. Seroprevalence increased during 2020; adolescents were primarily infected in the autumn/winter. Denmark has a high per capita test rate; roughly one undiagnosed infection of SARS-CoV-2 were estimated to occur for each diagnosed case. Approximately half were asymptomatically infected. The epidemic appears to have progressed relatively modestly during 2020 in Denmark.

Cross-border outbreak of Yersinia enterocolitica O3 associated with imported fresh spinach, Sweden and Denmark, March 2019

In April 2019, a cross-border outbreak of Yersinia entercolitica O3 was identified in Sweden and Denmark and confirmed using whole genome sequencing. Close cross-border collaboration with representatives from human and food authorities helped direct resources and investigations. Combined epidemiological and trace-back investigations pointed to imported fresh spinach as the outbreak vehicle and highlight that other vehicles of Y. enterocolitica outbreaks than pork should be considered.

Increasing incubation periods during a prolonged monophasic Salmonella Typhimurium outbreak with environmental contamination of a commercial kitchen at Oslo Airport, Norway, 2017

In September 2017, a cluster of monophasic Salmonella Typhimurium isolates was identified at the National Reference Laboratory for Enteropathogenic Bacteria in Norway. We investigated the cluster to identify the source and implement control measures. We defined a case as a person with laboratory-confirmed salmonellosis with the outbreak strain multiple locus variable-number tandem repeat analysis type. We conducted descriptive epidemiological and environmental investigations and performed whole genome sequencing (WGS) with core and accessory genome multilocus sequence typing of all isolates from cases or the environment connected with this outbreak. We identified 21 cases, residing in 10 geographically dispersed counties, all of whom had consumed food or drinks from a café at Oslo Airport. Case distribution by date of symptom onset suggested that a point source was introduced in mid-August followed by continued environmental contamination. The incubation periods ranged 0-16 days and increased as the outbreak progressed, likely due to increasingly low-dose exposure as control measures were implemented. WGS confirmed an identical cluster type-944 in all cases and six environmental specimens from the café. Control measures, including temporary closure and kitchen refurbishment, failed to eliminate the environmental source. We recommend strengthened hygiene measures for established environmental contamination during an outbreak.

Travel to Asia is a strong predictor for carriage of cephalosporin resistant E. coli and Klebsiella spp. but does not explain everything; prevalence study at a Norwegian hospital 2014-2016

Background

We aimed to estimate the prevalence of faecal carriage of extended-spectrum cephalosporin (ESC) resistant E. coli and K. pneumoniae (ESCr-EK) and vancomycin resistant enterococci (VRE) in patients upon hospital admission and identify factors associated with carriage to better target interventions and to guide empirical antibiotic treatment.

Methods

Between October 2014 and December 2016, we recruited patients admitted to a Norwegian university hospital. A rectal swab and questionnaire covering possible risk factors for colonisation were collected upon admission. Isolates were characterized by phenotypic methods. ESCr-EK isolates were subject to whole genome sequencing. We calculated prevalence and adjusted prevalence ratios (aPR) using binomial regression.

Results

Of 747 patients, 45 (6.0%) were colonised with ESCr-EK, none with VRE. The ESCr-EK isolates in 41 patients were multidrug resistant; no isolates were non-suceptible to meropenem. Prevalence of ESCr-EK was higher among travellers to Asia (aPR = 6.6; 95%CI 3.6–12; p < 0.001). No statistical significant difference in carriage was observed between departments, age or any other factors in the univariable analyses.

Conclusions

The observed prevalence of ESCr-EK colonisation upon admission was in the same range but lower than that reported in similar studies from Europe. Travel to Asia was a strong predictor for colonisation of ESCr-EK to be considered when administering empirical antimicrobial treatment. As less than one third of colonised patients had travelled to Asia, and no other factors investigated were found to be strongly associated with carriage, these findings underscore that healthcare personnel must apply standard infection control precautions for all patients.

Electronic supplementary material

The online version of this article (10.1186/s13756-018-0429-7) contains supplementary material, which is available to authorized users.

Estimates of global seasonal influenza-associated respiratory mortality: a modelling study

BACKGROUND

Estimates of influenza-associated mortality are important for national and international decision making on public health priorities. Previous estimates of 250 000-500 000 annual influenza deaths are outdated. We updated the estimated number of global annual influenza-associated respiratory deaths using country-specific influenza-associated excess respiratory mortality estimates from 1999-2015.

METHODS

We estimated country-specific influenza-associated respiratory excess mortality rates (EMR) for 33 countries using time series log-linear regression models with vital death records and influenza surveillance data. To extrapolate estimates to countries without data, we divided countries into three analytic divisions for three age groups (<65 years, 65-74 years, and ≥75 years) using WHO Global Health Estimate (GHE) respiratory infection mortality rates. We calculated mortality rate ratios (MRR) to account for differences in risk of influenza death across countries by comparing GHE respiratory infection mortality rates from countries without EMR estimates with those with estimates. To calculate death estimates for individual countries within each age-specific analytic division, we multiplied randomly selected mean annual EMRs by the country's MRR and population. Global 95% credible interval (CrI) estimates were obtained from the posterior distribution of the sum of country-specific estimates to represent the range of possible influenza-associated deaths in a season or year. We calculated influenza-associated deaths for children younger than 5 years for 92 countries with high rates of mortality due to respiratory infection using the same methods.

FINDINGS

EMR-contributing countries represented 57% of the global population. The estimated mean annual influenza-associated respiratory EMR ranged from 0·1 to 6·4 per 100 000 individuals for people younger than 65 years, 2·9 to 44·0 per 100 000 individuals for people aged between 65 and 74 years, and 17·9 to 223·5 per 100 000 for people older than 75 years. We estimated that 291 243-645 832 seasonal influenza-associated respiratory deaths (4·0-8·8 per 100 000 individuals) occur annually. The highest mortality rates were estimated in sub-Saharan Africa (2·8-16·5 per 100 000 individuals), southeast Asia (3·5-9·2 per 100 000 individuals), and among people aged 75 years or older (51·3-99·4 per 100 000 individuals). For 92 countries, we estimated that among children younger than 5 years, 9243-105 690 influenza-associated respiratory deaths occur annually.

INTERPRETATION

These global influenza-associated respiratory mortality estimates are higher than previously reported, suggesting that previous estimates might have underestimated disease burden. The contribution of non-respiratory causes of death to global influenza-associated mortality should be investigated.

FUNDING

None.

Excess all-cause and influenza-attributable mortality in Europe, December 2016 to February 2017

Since December 2016, excess all-cause mortality was observed in many European countries, especially among people aged ≥ 65 years. We estimated all-cause and influenza-attributable mortality in 19 European countries/regions. Excess mortality was primarily explained by circulation of influenza virus A(H3N2). Cold weather snaps contributed in some countries. The pattern was similar to the last major influenza A(H3N2) season in 2014/15 in Europe, although starting earlier in line with the early influenza season start.

The incidence of invasive pneumococcal serotype 3 disease in the Danish population is not reduced by PCV-13 vaccination

Since 2010, Denmark has included the 13-valent pneumococcal conjugated vaccine (PCV-13) in the childhood immunization programme. However, serotype 3 remains as an important cause of invasive pneumococcal disease (IPD) in Denmark. IPD surveillance data (1999-2016) was used to calculate the incidence and age-distribution of serotype 3 IPD, and the effect of PCV-13 on serotype 3 IPD incidence was examined. The incidence of serotype 3 IPD in the age group below 65 years was 0.51/100,000 pre PCV-13, and 0.45/100,000 post PCV-13. In the group 0-4 years, serotype 3 IPD incidence was 0.28/100,000 pre PCV-13, and 0.16/100,000 post PCV-13. Serotype 3 IPD incidence in the elderly showed a mean of 4.27/100,000 pre PCV-13, and 4.32/100,000 post PCV-13. PCV-13 childhood immunization in Denmark has not lead to a reduction of the incidence of IPD caused by serotype 3. The reason behind this missing effect needs to be investigated further.

Improving national surveillance of Lyme neuroborreliosis in Denmark through electronic reporting of specific antibody index testing from 2010 to 2012

Our aim was to evaluate the results of automated surveillance of Lyme neuroborreliosis (LNB) in Denmark using the national microbiology database (MiBa), and to describe the epidemiology of laboratory-confirmed LNB at a national level. MiBa-based surveillance includes electronic transfer of laboratory results, in contrast to the statutory surveillance based on manually processed notifications. Antibody index (AI) testing is the recommend laboratory test to support the diagnosis of LNB in Denmark. In the period from 2010 to 2012, 217 clinical cases of LNB were notified to the statutory surveillance system, while 533 cases were reported AI positive by the MiBa system. Thirty-five unconfirmed cases (29 AI-negative and 6 not tested) were notified, but not captured by MiBa. Using MiBa, the number of reported cases was increased almost 2.5 times. Furthermore, the reporting was timelier (median lag time: 6 vs 58 days). Average annual incidence of AI-confirmed LNB in Denmark was 3.2/100,000 population and incidences stratified by municipality ranged from none to above 10/100,000. This is the first study reporting nationwide incidence of LNB using objective laboratory criteria. Laboratory-based surveillance with electronic data-transfer was more accurate, complete and timely compared to the surveillance based on manually processed notifications. We propose using AI test results for LNB surveillance instead of clinical reporting.

Excess mortality among the elderly in European countries, December 2014 to February 2015

Since December 2014 and up to February 2015, the weekly number of excess deaths from all-causes among individuals?≥?65 years of age in 14 European countries have been significantly higher than in the four previous winter seasons. The rise in unspecified excess mortality coincides with increased proportion of influenza detection in the European influenza surveillance schemes with a main predominance of influenza A(H3N2) viruses seen throughout Europe in the current season, though cold snaps and other respiratory infections may also have had an effect.

Socioeconomic position and the risk of spontaneous abortion: a study within the Danish National Birth Cohort

OBJECTIVES

To investigate the relationship between different indicators of socioeconomic position and the risk of spontaneous abortion.

DESIGN

Cohort study.

SETTING

1996-2002, Denmark.

PARTICIPANTS

All first time participants, a total of 89 829 pregnant women, enrolled in the Danish National Birth Cohort were included in the present study. Overall, 4062 pregnancies ended in spontaneous abortion. Information on education, income and labour market attachment in the year before pregnancy was drawn from national registers.

MAIN OUTCOME MEASURE

Spontaneous abortion, that is, fetal death within the first 22 weeks of pregnancy, was the outcome of interest. The authors estimated HRs of spontaneous abortion using Cox regression analysis with gestational age as the underlying time scale.

RESULTS

Women with <10 years of education had an elevated risk of spontaneous abortion when compared with women with >12 years of education (HR 1.19 (95% CI 1.05 to 1.34)). The HR estimates for the four lowest income quintiles were all increased (HRs between 1.09 and 1.15) as compared with the upper quintile but did not differ considerably from each other. In general, no statistically significant association was found between labour market attachment and the risk of spontaneous abortion; however, the group of women on disability pension had an increased HR of spontaneous abortion when compared with women who were employed (HR 1.32 (95% CI 0.82 to 2.13)).

CONCLUSIONS

Educational level and income were inversely associated with the risk of spontaneous abortion. As these factors most likely are non-causally related to spontaneous abortion, the findings indicate that factors related to social position, probably of the environmental and behavioural type, may affect spontaneous abortion risk. The study highlights the need for studies addressing such exposures in order to prevent spontaneous abortions.