Incidence of Invasive and Noninvasive Pneumococcal Pneumonia Hospitalizations in People Aged ≥50 Years: Assessing Variability Across Denmark and Spain.

Determining pneumococcal pneumonia (PP) burden in the elderly population is challenging due to limited data on invasive PP (IPP) and, in particular, noninvasive PP (NIPP) incidence. Using retrospective cohorts of adults aged ≥50 years in Denmark (2 782 303) and the Valencia region, Spain (2 283 344), we found higher IPP hospitalization rates in Denmark than Valencia (18.3 vs 9/100 000 person-years [PY], respectively). Conversely, NIPP hospitalization rates were higher in Valencia (48.2 vs 7.2/100 000 PY). IPP and NIPP rates increased with age and comorbidities in both regions, with variations by sex and case characteristics (eg, complications, mortality). The burden of PP in adults is substantial, yet its true magnitude remains elusive. Discrepancies in clinical practices impede international comparisons; for instance, Valencia employed a higher frequency of urinary antigen tests compared to Denmark. Additionally, coding practices and prehospital antibiotic utilization may further influence these variations. These findings could guide policymakers and enhance the understanding of international disparities in disease burden assessments.

Mycoplasma pneumoniae epidemic in Denmark, October to December, 2023.

We report a surge of patients, especially children and adolescents, with respiratory disease caused by Mycoplasma pneumoniae in Denmark since October 2023. While the surge has reached an epidemic level, no impact on hospital capacity has been observed; only 14% (446/3,195) of cases, primarily adults, required hospitalisation. Macrolide resistance was detected in less than 2% of samples tested. Timely monitoring of hospitalisations linked to M. pneumoniae infections has been established to inform the healthcare system, decisionmakers and the public.

Pertussis epidemic in Denmark, August 2023 to February 2024.

We report a record high pertussis epidemic in Denmark since August 2023. Highest incidence was in adolescents, while peak incidence in infants was lower vs previous epidemics in 2019 and 2016. Among infants aged 0-2 months, over half (29/48) were hospitalised and one infant died, underlining the disease severity in the youngest. To protect infants, pertussis vaccination in pregnant women was introduced in January 2024 in the national vaccination programme. Improved vaccination surveillance in pregnant women is being implemented.

Age-dependent influenza infection patterns and subtype circulation in Denmark, in seasons 2015/16 to 2021/22.

BackgroundInfluenza was almost absent for 2 years following the implementation of strict public health measures to prevent the spread of SARS-CoV-2. The consequence of this on infections in different age groups is not yet known.AimTo describe the age groups infected with the influenza virus in 2021/22, the first post-pandemic influenza season in Denmark, compared with the previous six seasons, and subtypes circulating therein.MethodsInfection and hospitalisation incidences per season and age group were estimated from data in Danish registries. Influenza virus subtypes and lineages were available from samples sent to the National Influenza Centre at Statens Serum Institut.ResultsTest incidence followed a similar pattern in all seasons, being highest in 0-1-year-olds and individuals over 75 years, and lowest in 7-14-year-olds and young people 15 years to late twenties. When the influenza A virus subtypes A(H3N2) and A(H1N1)pdm09 co-circulated in seasons 2015/16 and 2017/18 to 2019/20, the proportion of A(H1N1)pdm09 was higher in 0-1-year-olds and lower in the over 85-year-olds compared with the overall proportion of A(H1N1)pdm09 in these seasons. The proportion of A(H3N2) was higher in the over 85 years age group compared with the overall proportion of A(H3N2). The 2016/17 and 2021/22 seasons were dominated by A(H3N2) but differed in age-specific trends, with the over 85 years age group initiating the 2016/17 season, while the 2021/22 season was initiated by the 15-25-year-olds, followed by 7-14-year-olds.ConclusionThe 2021/22 influenza season had a different age distribution compared with pre-COVID-19 pandemic seasons.

Effectiveness of historical smallpox vaccination against mpox clade II in men in Denmark, France, the Netherlands and Spain, 2022.

BackgroundIn 2022, a global monkeypox virus (MPXV) clade II epidemic occurred mainly among men who have sex with men. Until early 1980s, European smallpox vaccination programmes were part of worldwide smallpox eradication efforts. Having received smallpox vaccine > 20 years ago may provide some cross-protection against MPXV.AimTo assess the effectiveness of historical smallpox vaccination against laboratory-confirmed mpox in 2022 in Europe.MethodsEuropean countries with sufficient data on case vaccination status and historical smallpox vaccination coverage were included. We selected mpox cases born in these countries during the height of the national smallpox vaccination campaigns (latest 1971), male, with date of onset before 1 August 2022. We estimated vaccine effectiveness (VE) and corresponding 95% CI for each country using logistic regression as per the Farrington screening method. We calculated a pooled estimate using a random effects model.ResultsIn Denmark, France, the Netherlands and Spain, historical smallpox vaccination coverage was high (80-90%) until the end of the 1960s. VE estimates varied widely (40-80%, I2 = 82%), possibly reflecting different booster strategies. The pooled VE estimate was 70% (95% CI: 23-89%).ConclusionOur findings suggest residual cross-protection by historical smallpox vaccination against mpox caused by MPXV clade II in men with high uncertainty and heterogeneity. Individuals at high-risk of exposure should be offered mpox vaccination, following national recommendations, regardless of prior smallpox vaccine history, until further evidence becomes available. There is an urgent need to conduct similar studies in sub-Saharan countries currently affected by the MPXV clade I outbreak.

Relative vaccine effectiveness against COVID-19 hospitalisation in persons aged ≥ 65 years: results from a VEBIS network, Europe, October 2021 to July 2023.

To monitor relative vaccine effectiveness (rVE) against COVID-19-related hospitalisation of the first, second and third COVID-19 booster (vs complete primary vaccination), we performed monthly Cox regression models using retrospective cohorts constructed from electronic health registries in eight European countries, October 2021-July 2023. Within 12 weeks of administration, each booster showed high rVE (≥ 70% for second and third boosters). However, as of July 2023, most of the relative benefit has waned, particularly in persons ≥ 80-years-old, while some protection remained in 65-79-year-olds.

Outcomes following SARS-CoV-2 infection in individuals with and without inflammatory rheumatic diseases: a Danish nationwide cohort study.

OBJECTIVE: In a setting with an extensive SARS-CoV-2 test strategy and availability of effective vaccines, we aimed to investigate if patients with inflammatory rheumatic diseases (IRD) face greater risk of contracting SARS-CoV-2 and have a worse prognosis of increased risk of hospitalisation, assisted ventilation and death compared with the general population. METHODS: This was a nationwide, population-based register study that compared outcomes of SARS-CoV-2 infection in Danish patients with IRD (n=66 840) with matched population controls (n=668 400). The study period was from March 2020 to January 2023. Cox regression analyses were used to calculate incidence rate ratios (IRRs) for SARS-CoV-2-related outcomes. RESULTS: We observed a difference in time to first and second positive SARS-CoV-2 test in patients with IRD compared with the general population (IRR 1.06, 95% CI 1.05 to 1.07) and (IRR 1.21, 95% CI 1.15 to 1.27). The risks of hospital contact with COVID-19 and severe COVID-19 were increased in patients with IRD compared with population controls (IRR 2.11, 95% CI 1.99 to 2.23) and (IRR 2.18, 95% CI 1.94 to 2.45). The risks of assisted ventilation (IRR 2.33, 95% CI 1.89 to 2.87) and COVID-19 leading to death were increased (IRR 1.98, 95% CI 1.69 to 2.33). Patients with IRD had more comorbidities compared with the general population. A third SARS-CoV-2 vaccination was associated with a reduced need for hospitalisation with COVID-19 and reduced the risk of death. CONCLUSION: Patients with IRD have a risk of SARS-CoV-2, which nearly corresponds to the general population but had a substantial increased risk of hospitalisation with COVID-19, severe COVID-19, requiring assisted ventilation and COVID-19 leading to death, especially in patients with comorbidities.

Sociodemographic differences in Covid-19 vaccine uptake in Denmark: a nationwide register-based cohort study.

BACKGROUND: Covid-19 vaccination is the main strategy to reduce SARS-CoV-2 transmission, mortality and morbidity. This study aimed to examine sociodemographic differences in Covid-19 vaccine uptake among all individuals invited for Covid-19 vaccination in Denmark. METHODS: This study was designed as a nationwide register-based cohort study. The study population included all Danish residents aged 12 years or above in Denmark between December 27, 2020 and October 20, 2021. Individuals who died during the study period before receiving an invitation for Covid-19 vaccination were excluded. Associations between sociodemographic factors and Covid-19 vaccination uptake were analyzed using logistic regression models adjusting for age, sex, immigration status, educational level, disposable income and history of SARS-CoV-2 infection. RESULTS: The study population included 5,164,558 individuals. The overall vaccination coverage was 87.1% by October 20, 2021. In the full adjusted logistic regression models, the highest ORs for non-vaccination were observed among individuals aged 12-24 years (OR: 8.99 (95% CI: 8.76-9.23)), descendants of non-western immigrants (OR: 5.26 (95% CI: 5.18-5.33)), individuals who never had a PCR-test performed (OR: 2.93 (95% CI: 2.90-2.96)), individuals with primary school as highest completed educational level (OR: 2.87 (95% CI: 2.83-2.91)) and individuals with disposable income < 33,605 EUR (OR: 3.72 (95% CI: 3.52-3.93)). CONCLUSION: Overall, the Covid-19 vaccine uptake was high in Denmark. However, large sociodemographic differences in the vaccine uptake exist. The youngest age groups had the lowest vaccination coverage. Furthermore, the impact of the sociodemographic factors was more pronounced in the youngest age groups. The identified determinants may be used to design policies to help maximize the vaccination coverage.

Early and intense epidemic of respiratory syncytial virus (RSV) in Denmark, August to December 2022.

In the autumn of 2022, Denmark witnessed the second out-of-season epidemic of respiratory syncytial virus (RSV) following widespread societal preventive measures implemented against the coronavirus disease (COVID-19) pandemic during 2020 and 2021. Admissions peaked at twice the level of pre-pandemic seasons. Especially infants below 6 months of age were affected, but also adults over 45 years of age. The current epidemic is dominated by RSV subtype B, unlike the major RSV summer epidemic in 2021 dominated by RSV subtype A.

Interim 2022/23 influenza vaccine effectiveness: six European studies, October 2022 to January 2023.

BackgroundBetween October 2022 and January 2023, influenza A(H1N1)pdm09, A(H3N2) and B/Victoria viruses circulated in Europe with different influenza (sub)types dominating in different areas.AimTo provide interim 2022/23 influenza vaccine effectiveness (VE) estimates from six European studies, covering 16 countries in primary care, emergency care and hospital inpatient settings.MethodsAll studies used the test-negative design, but with differences in other study characteristics, such as data sources, patient selection, case definitions and included age groups. Overall and influenza (sub)type-specific VE was estimated for each study using logistic regression adjusted for potential confounders.ResultsThere were 20,477 influenza cases recruited across the six studies, of which 16,589 (81%) were influenza A. Among all ages and settings, VE against influenza A ranged from 27 to 44%. Against A(H1N1)pdm09 (all ages and settings), VE point estimates ranged from 28% to 46%, higher among children (< 18 years) at 49-77%. Against A(H3N2), overall VE ranged from 2% to 44%, also higher among children (62-70%). Against influenza B/Victoria, overall and age-specific VE were ≥ 50% (87-95% among children < 18 years).ConclusionsInterim results from six European studies during the 2022/23 influenza season indicate a ≥ 27% and ≥ 50% reduction in disease occurrence among all-age influenza vaccine recipients for influenza A and B, respectively, with higher reductions among children. Genetic virus characterisation results and end-of-season VE estimates will contribute to greater understanding of differences in influenza (sub)type-specific results across studies.

Vaccine effectiveness against SARS-CoV-2 reinfection during periods of Alpha, Delta, or Omicron dominance: A Danish nationwide study.

BACKGROUND: Individuals with a prior Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection have a moderate to high degree of protection against reinfection, though seemingly less so when the Omicron variant of SARS-CoV-2 started to circulate. The aim of this study was to evaluate the vaccine effectiveness (VE) against SARS-CoV-2 reinfection, Coronavirus Disease 2019 (COVID-19)-related hospitalization, and COVID-19-related death, in individuals with prior SARS-CoV-2 infection, and to assess the effect of time since vaccination during periods with different dominant SARS-CoV-2 variants. METHODS AND FINDINGS: This study used a nationwide cohort design including all individuals with a confirmed SARS-CoV-2 infection, who were alive, and residing in Denmark between 1 January 2020 and 31 January 2022. Using Danish nationwide registries, we obtained information on SARS-CoV-2 infections, COVID-19 vaccination, age, sex, comorbidity, staying at hospital, and country of origin. The study population included were individuals with prior SARS-CoV-2 infection. Estimates of VE against SARS-CoV-2 reinfection with 95% confidence intervals (CIs) were calculated using a Poisson regression model and adjusted for age, sex, country of origin, comorbidity, staying at hospital, calendar time, and test incidence using a Cox regression model. The VE estimates were calculated separately for three periods with different dominant SARS-CoV-2 variants (Alpha (B.1.1.7), Delta (B.1.617.2), or Omicron (B.1.1.529)) and by time since vaccination using unvaccinated as the reference. In total, 148,527 person-years and 44,192 SARS-CoV-2 infections were included for the analysis regarding reinfections. The study population comprised of 209,814 individuals infected before or during the Alpha period, 292,978 before or during the Delta period, and 245,530 before or during the Omicron period. Of these, 40,281 individuals had completed their primary vaccination series during the Alpha period (19.2%), 190,026 during the Delta period (64.9%), and 158,563 during the Omicron period (64.6%). VE against reinfection following any COVID-19 vaccine type administered in Denmark, peaked at 71% (95% CI: -Inf to 100%) at 104 days or more after vaccination during the Alpha period, 94% (95% CI: 92% to 96%) 14 to 43 days after vaccination during the Delta period, and 60% (95% CI: 58% to 62%) 14 to 43 days after vaccination during the Omicron period. Waning immunity following vaccination was observed and was most pronounced during the Omicron period. Due to too few events, it was not possible to estimate VE for hospitalization and death. Study limitations include potentially undetected reinfections, differences in health-seeking behavior, or risk behavior between the compared groups. CONCLUSIONS: This study shows that in previously infected individuals, completing a primary vaccination series was associated with a significant protection against SARS-CoV-2 reinfection compared with no vaccination. Even though vaccination seems to protect to a lesser degree against reinfection with the Omicron variant, these findings are of public health relevance as they show that previously infected individuals still benefit from COVID-19 vaccination in all three variant periods.

Vaccine effectiveness against SARS-CoV-2 infection or COVID-19 hospitalization with the Alpha, Delta, or Omicron SARS-CoV-2 variant: A nationwide Danish cohort study.

BACKGROUND: The continued occurrence of more contagious Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) variants and waning immunity over time require ongoing reevaluation of the vaccine effectiveness (VE). This study aimed to estimate the effectiveness in 2 age groups (12 to 59 and 60 years or above) of 2 or 3 vaccine doses (BNT162b2 mRNA or mRNA-1273) by time since vaccination against SARS-CoV-2 infection and Coronavirus Disease 2019 (COVID-19) hospitalization in an Alpha-, Delta-, or Omicron-dominated period. METHODS AND FINDINGS: A Danish nationwide cohort study design was used to estimate VE against SARS-CoV-2 infection and COVID-19 hospitalization with the Alpha, Delta, or Omicron variant. Information was obtained from nationwide registries and linked using a unique personal identification number. The study included all previously uninfected residents in Denmark aged 12 years or above (18 years or above for the analysis of 3 doses) in the Alpha (February 20 to June 15, 2021), Delta (July 4 to November 20, 2021), and Omicron (December 21, 2021 to January 31, 2022) dominated periods. VE estimates including 95% confidence intervals (CIs) were calculated (1-hazard ratio∙100) using Cox proportional hazard regression models with underlying calendar time and adjustments for age, sex, comorbidity, and geographical region. Vaccination status was included as a time-varying exposure. In the oldest age group, VE against infection after 2 doses was 90.7% (95% CI: 88.2; 92.7) for the Alpha variant, 82.3% (95% CI: 75.5; 87.2) for the Delta variant, and 39.9% (95% CI: 26.3; 50.9) for the Omicron variant 14 to 30 days since vaccination. The VE waned over time and was 73.2% (Alpha, 95% CI: 57.1; 83.3), 50.0% (Delta, 95% CI: 46.7; 53.0), and 4.4% (Omicron, 95% CI: -0.1; 8.7) >120 days since vaccination. Higher estimates were observed after the third dose with VE estimates against infection of 86.1% (Delta, 95% CI: 83.3; 88.4) and 57.7% (Omicron, 95% CI: 55.9; 59.5) 14 to 30 days since vaccination. Among both age groups, VE against COVID-19 hospitalization 14 to 30 days since vaccination with 2 or 3 doses was 98.1% or above for the Alpha and Delta variants. Among both age groups, VE against COVID-19 hospitalization 14 to 30 days since vaccination with 2 or 3 doses was 95.5% or above for the Omicron variant. The main limitation of this study is the nonrandomized study design including potential differences between the unvaccinated (reference group) and vaccinated individuals. CONCLUSIONS: Two vaccine doses provided high protection against SARS-CoV-2 infection and COVID-19 hospitalization with the Alpha and Delta variants with protection, notably against infection, waning over time. Two vaccine doses provided only limited and short-lived protection against SARS-CoV-2 infection with Omicron. However, the protection against COVID-19 hospitalization following Omicron SARS-CoV-2 infection was higher. The third vaccine dose substantially increased the level and duration of protection against infection with the Omicron variant and provided a high level of sustained protection against COVID-19 hospitalization among the +60-year-olds.

COVID-19 preventive measures coincided with a marked decline in other infectious diseases in Denmark, spring 2020.

We aimed to descriptively analyse the possible impact of the national COVID-19 interventions on the incidence of common infectious diseases in Denmark during spring and summer 2020. This observational study focused on national register data on infections caused by 16 different bacterial and viral pathogens. We included new cases registered between 1 January 2016 and 31 July 2020. The weekly number of new cases were analysed with respect to the COVID-19-related interventions introduced during 2020. We found a marked decrease in infections associated with droplet transmission coinciding with the COVID-19 interventions in spring and summer 2020. These included decreases in both viral and bacterial airway infections and also decreases in invasive infections caused by Streptococcus pneumoniae, Haemophilus influenzae and Neisseria meningitidis. There was also a reduction in cases associated with foodborne transmission during the COVID-19 lockdown period. We found no effect of the lockdown on infections by invasive beta-haemolytic streptococci group B, C and G, Staphylococcus aureus bacteraemia, Neisseria gonorrhoeae or Clostridioides difficile. In conclusion, we found that the widespread interventions such as physical distancing, less travel, hygiene measures and lockdown of schools, restaurants and workplaces together coincided with a marked decline in respiratory infections and, to a smaller extent, some foodborne-transmitted infections.

A late sharp increase in influenza detections and low interim vaccine effectiveness against the circulating A(H3N2) strain, Denmark, 2021/22 influenza season up to 25 March 2022.

We estimated interim influenza A vaccine effectiveness (VE) following a late sharp rise in cases during an influenza A(H3N2)-dominated 2021/22 season, after lifting COVID-19 restrictions. In children aged 2-6 years offered a live attenuated influenza vaccine, adjusted VE was 62.7% (95% CI: 10.9-84.4) in hospitalised and 64.2% (95% CI: 50.5-74.1) in non-hospitalised children. In non-hospitalised patients aged 7-44 years, VE was 24.8% (95% CI: 12.8-35.2); VE was non-significant in remaining age groups and hospital/non-hospital settings.

Estimation of COVID-19 vaccine effectiveness against hospitalisation in individuals aged ≥ 65 years using electronic health registries; a pilot study in four EU/EEA countries, October 2021 to March 2022.

By employing a common protocol and data from electronic health registries in Denmark, Navarre (Spain), Norway and Portugal, we estimated vaccine effectiveness (VE) against hospitalisation due to COVID-19 in individuals aged ≥ 65 years old, without previous documented infection, between October 2021 and March 2022. VE was higher in 65-79-year-olds compared with ≥ 80-year-olds and in those who received a booster compared with those who were primary vaccinated. VE remained high (ca 80%) between ≥ 12 and < 24 weeks after the first booster administration, and after Omicron became dominant.

Vaccine effectiveness against SARS-CoV-2 infection, hospitalization, and death when combining a first dose ChAdOx1 vaccine with a subsequent mRNA vaccine in Denmark: A nationwide population-based cohort study.

BACKGROUND: The recommendations in several countries to stop using the ChAdOx1 vaccine has led to vaccine programs combining different Coronavirus Disease 2019 (COVID-19) vaccine types, which necessitates knowledge on vaccine effectiveness (VE) of heterologous vaccine schedules. The aim of this Danish nationwide population-based cohort study was therefore to estimate the VE against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection and COVID-19-related hospitalization and death following the first dose of the ChAdOx1 vaccine and the combination of the ChAdOx1/mRNA vaccines. METHODS AND FINDINGS: All individuals alive in or immigrating to Denmark from 9 February 2021 to 23 June 2021 were identified in the Danish Civil Registration System. Information on exposure, outcomes, and covariates was obtained from Danish national registries. Poisson and Cox regression models were used to calculate crude and adjusted VE, respectively, along with 95% confidence intervals (CIs) against SARS-CoV-2 infection and COVID-19-related hospitalization or death comparing vaccinated versus unvaccinated individuals. The VE estimates were adjusted for calendar time as underlying time and for sex, age, comorbidity, country of origin, and hospital admission. The analyses included 5,542,079 individuals (97.6% of the total Danish population). A total of 144,360 individuals were vaccinated with the ChAdOx1 vaccine as the first dose, and of these, 136,551 individuals received an mRNA vaccine as the second dose. A total of 1,691,464 person-years and 83,034 SARS-CoV-2 infections were included. The individuals vaccinated with the first dose of the ChAdOx1 vaccine dose had a median age of 45 years. The study population was characterized by an equal distribution of males and females; 6.7% and 9.2% originated from high-income and other countries, respectively. The VE against SARS-CoV-2 infection when combining the ChAdOx1 and an mRNA vaccine was 88% (95% CI: 83; 92) 14 days after the second dose and onwards. There were no COVID-19-related hospitalizations or deaths among the individuals vaccinated with the combined vaccine schedule during the study period. Study limitations including unmeasured confounders such as risk behavior and increasing overall vaccine coverage in the general population creating herd immunity are important to take into consideration when interpreting the results. CONCLUSIONS: In this study, we observed a large reduction in the risk of SARS-CoV-2 infection when combining the ChAdOx1 and an mRNA vaccine, compared with unvaccinated individuals.

Recommendations for respiratory syncytial virus surveillance at the national level.

Respiratory syncytial virus (RSV) is a common cause of acute lower respiratory tract infections and hospitalisations among young children and is globally responsible for many deaths in young children, especially in infants aged <6 months. Furthermore, RSV is a common cause of severe respiratory disease and hospitalisation among older adults. The development of new candidate vaccines and monoclonal antibodies highlights the need for reliable surveillance of RSV. In the European Union (EU), no up-to-date general recommendations on RSV surveillance are currently available. Based on outcomes of a workshop with 29 European experts in the field of RSV virology, epidemiology and public health, we provide recommendations for developing a feasible and sustainable national surveillance strategy for RSV that will enable harmonisation and data comparison at the European level. We discuss three surveillance components: active sentinel community surveillance, active sentinel hospital surveillance and passive laboratory surveillance, using the EU acute respiratory infection and World Health Organization (WHO) extended severe acute respiratory infection case definitions. Furthermore, we recommend the use of quantitative reverse transcriptase PCR-based assays as the standard detection method for RSV and virus genetic characterisation, if possible, to monitor genetic evolution. These guidelines provide a basis for good quality, feasible and affordable surveillance of RSV. Harmonisation of surveillance standards at the European and global level will contribute to the wider availability of national level RSV surveillance data for regional and global analysis, and for estimation of RSV burden and the impact of future immunisation programmes.

Abrupt termination of the 2019/20 influenza season following preventive measures against COVID-19 in Denmark, Norway and Sweden.

BackgroundIn mid-March 2020, a range of public health and social measures (PHSM) against the then new coronavirus disease (COVID-19) were implemented in Denmark, Norway and Sweden.AimWe analysed the development of influenza cases during the implementation of PHSM against SARS-CoV-2 in the Scandinavian countries.MethodBased on the established national laboratory surveillance of influenza, we compared the number of human influenza cases in the weeks immediately before and after the implementation of SARS-CoV-2 PHSM by country. The 2019/20 influenza season was compared with the five previous seasons.ResultsA dramatic reduction in influenza cases was seen in all three countries, with only a 3- to 6-week duration from the peak of weekly influenza cases until the percentage dropped below 1%. In contrast, in the previous nine influenza seasons, the decline from the seasonal peak to below 1% of influenza-positive samples took more than 10 weeks.ConclusionsThe PHSM against SARS-CoV-2 were followed by a dramatic reduction in influenza cases, indicating a wider public health effect of the implemented measures.

Spotlight influenza: Influenza surveillance before and after the introduction of point-of-care testing in Denmark, season 2014/15 to 2018/19.

BackgroundIn Denmark, influenza surveillance is ensured by data capturing from existing population-based registers. Since 2017, point-of-care (POC) testing has been implemented outside the regional clinical microbiology departments (CMD).AimWe aimed to assess influenza laboratory results in view of the introduction of POC testing.MethodsWe retrospectively observed routine surveillance data on national influenza tests before and after the introduction of POC testing as available in the Danish Microbiological Database. Also, we conducted a questionnaire study among Danish CMD about influenza diagnostics.ResultsBetween the seasons 2014/15 and 2018/19, 199,744 influenza tests were performed in Denmark of which 44,161 were positive (22%). After the introduction of POC testing, the overall percentage of positive influenza tests per season did not decrease. The seasonal influenza test incidence was higher in all observed age groups. The number of operating testing platforms placed outside a CMD and with an instrument analytical time ≤ 3 h increased after 2017. Regionally, the number of tests registered as POC in the Danish Microbiological Database and the number of tests performed with an instrument analytical time ≤ 3 h or outside a CMD partially differed. Where comparable (71% of tests), the relative proportion of POC tests out of all tests increased from season 2017/18 to 2018/19. In both seasons, the percentage of positive POC tests resulted slightly lower than for non-POC tests.ConclusionPOC testing integrated seamlessly into national influenza surveillance. We propose the use of POC results in the routine surveillance of seasonal influenza.

Acute myocardial infarctions and stroke triggered by laboratory-confirmed respiratory infections in Denmark, 2010 to 2016.

BackgroundSeveral studies have investigated a possible association between respiratory infection and acute myocardial infarction (MI). As both influenza and pneumococcal infections are vaccine preventable, understanding the populations affected by virus-induced cardiovascular complications is important to guide public health and clinical practice.AimThis observational study aimed to quantify the association between laboratory-confirmed respiratory bacteria or virus infections and risk of first MI or stroke, by using self-controlled case series (SCCS) analysis of anonymised linked electronic Danish health records.MethodsThe SCCS method was used to determine the relative incidence of the first event of MI and stroke occurring within 28 days after laboratory-confirmed respiratory infections compared with the baseline time period.ResultsIn the age and season adjusted analyses for first acute MI, the incidence ratios (IR) of a MI event occurring during the risk period were significantly elevated following a Streptococcus pneumoniae infection with values of 20.1, 11.0 and 4.9 during 1-3, 4-7 and 8-14 days, respectively and following respiratory virus infection with values of 15.2, 4.5 and 4.4 during 1-3, 8-14 and 15-28 days, respectively. The significantly elevated IRs for stroke following an S. pneumoniae infection were 25.5 and 6.3 during 1-3 and 8-14 days, respectively and following respiratory virus infection 8.3, 7.8 and 6.2 during 1-3, 4-7 and 8-14 days, respectively.ConclusionThis study suggested a significant cardiovascular event triggering effect following infection with S. pneumoniae and respiratory viruses (mainly influenza), indicating the importance of protection against vaccine-preventable respiratory infections.