Participatory, Virologic, and Wastewater Surveillance Data to Assess Underestimation of COVID-19 Incidence, Germany, 2020-2024.

Using participatory, virologic, and wastewater surveillance systems, we estimated when and to what extent reported data of adult COVID-19 cases underestimated COVID-19 incidence in Germany. We also examined how case underestimation evolved over time. Our findings highlight how community-based surveillance systems can complement official notification systems for respiratory disease dynamics.

Atypical age distribution and high disease severity in children with RSV infections during two irregular epidemic seasons throughout the COVID-19 pandemic, Germany, 2021 to 2023.

BackgroundNon-pharmaceutical interventions (NPIs) during the COVID-19 pandemic affected respiratory syncytial virus (RSV) circulation worldwide.AimTo describe, for children aged < 5 years, the 2021 and 2022/23 RSV seasons in Germany.MethodsThrough data and 16,754 specimens from outpatient sentinel surveillance, we investigated RSV seasonality, circulating lineages, and affected children's age distributions in 2021 and 2022/23. Available information about disease severity from hospital surveillance was analysed for patients with RSV-specific diagnosis codes (n = 13,104). Differences between RSV seasons were assessed by chi-squared test and age distributions trends by Mann-Kendall test.ResultsRSV seasonality was irregular in 2021 (weeks 35-50) and 2022/23 (weeks 41-3) compared to pre-COVID-19 2011/12-2019/20 seasons (median weeks 51-12). RSV positivity rates (RSV-PR) were higher in 2021 (40% (522/1,291); p < 0.001) and 2022/23 (30% (299/990); p = 0.005) than in prior seasons (26% (1,430/5,511)). Known globally circulating RSV-A (lineages GA2.3.5 and GA2.3.6b) and RSV-B (lineage GB5.0.5a) strains, respectively, dominated in 2021 and 2022/23. In 2021, RSV-PRs were similar in 1 - < 2, 2 - < 3, 3 - < 4, and 4 - < 5-year-olds. RSV hospitalisation incidence in 2021 (1,114/100,000, p < 0.001) and in 2022/23 (1,034/100,000, p < 0.001) was approximately double that of previous seasons' average (2014/15-2019/20: 584/100,000). In 2022/23, proportions of RSV patients admitted to intensive care units rose (8.5% (206/2,413)) relative to pre-COVID-19 seasons (6.8% (551/8,114); p = 0.004), as did those needing ventilator support (6.1% (146/2,413) vs 3.8% (310/8,114); p < 0.001).ConclusionsHigh RSV-infection risk in 2-4-year-olds in 2021 and increased disease severity in 2022/23 possibly result from lower baseline population immunity, after NPIs diminished exposure to RSV.

COVID-19 vaccine effectiveness against symptomatic infection with SARS-CoV-2 BA.1/BA.2 lineages among adults and adolescents in a multicentre primary care study, Europe, December 2021 to June 2022.

BackgroundScarce European data in early 2021 suggested lower vaccine effectiveness (VE) against SARS-CoV-2 Omicron lineages than previous variants.AimWe aimed to estimate primary series (PS) and first booster VE against symptomatic BA.1/BA.2 infection and investigate potential biases.MethodsThis European test-negative multicentre study tested primary care patients with acute respiratory symptoms for SARS-CoV-2 in the BA.1/BA.2-dominant period. We estimated PS and booster VE among adults and adolescents (PS only) for all products combined and for Comirnaty alone, by time since vaccination, age and chronic condition. We investigated potential bias due to correlation between COVID-19 and influenza vaccination and explored effect modification and confounding by prior SARS-CoV-2 infection.ResultsAmong adults, PS VE was 37% (95% CI: 24-47%) overall and 60% (95% CI: 44-72%), 43% (95% CI: 26-55%) and 29% (95% CI: 13-43%) < 90, 90-179 and ≥ 180 days post vaccination, respectively. Booster VE was 42% (95% CI: 32-51%) overall and 56% (95% CI: 47-64%), 22% (95% CI: 2-38%) and 3% (95% CI: -78% to 48%), respectively. Primary series VE was similar among adolescents. Restricting analyses to Comirnaty had little impact. Vaccine effectiveness was higher among older adults. There was no signal of bias due to correlation between COVID-19 and influenza vaccination. Confounding by previous infection was low, but sample size precluded definite assessment of effect modification.ConclusionPrimary series and booster VE against symptomatic infection with BA.1/BA.2 ranged from 37% to 42%, with similar waning post vaccination. Comprehensive data on previous SARS-CoV-2 infection would help disentangle vaccine- and infection-induced immunity.

Interim 2023/24 influenza A vaccine effectiveness: VEBIS European primary care and hospital multicentre studies, September 2023 to January 2024.

Influenza A viruses circulated in Europe from September 2023 to January 2024, with influenza A(H1N1)pdm09 predominance. We provide interim 2023/24 influenza vaccine effectiveness (IVE) estimates from two European studies, covering 10 countries across primary care (EU-PC) and hospital (EU-H) settings. Interim IVE was higher against A(H1N1)pdm09 than A(H3N2): EU-PC influenza A(H1N1)pdm09 IVE was 53% (95% CI: 41 to 63) and 30% (95% CI: -3 to 54) against influenza A(H3N2). For EU-H, these were 44% (95% CI: 30 to 55) and 14% (95% CI: -32 to 43), respectively.

SARS-CoV-2 Omicron variants BA.1 and BA.2 both show similarly reduced disease severity of COVID-19 compared to Delta, Germany, 2021 to 2022.

German national surveillance data analysis shows that hospitalisation odds associated with Omicron lineage BA.1 or BA.2 infections are up to 80% lower than with Delta infection, primarily in ≥ 35-year-olds. Hospitalised vaccinated Omicron cases' proportions (2.3% for both lineages) seemed lower than those of the unvaccinated (4.4% for both lineages). Independent of vaccination status, the hospitalisation frequency among cases with Delta seemed nearly threefold higher (8.3%) than with Omicron (3.0% for both lineages), suggesting that Omicron inherently causes less severe disease.

Using routine emergency department data for syndromic surveillance of acute respiratory illness, Germany, week 10 2017 until week 10 2021.

BackgroundThe COVID-19 pandemic expanded the need for timely information on acute respiratory illness at population level.AimWe explored the potential of routine emergency department data for syndromic surveillance of acute respiratory illness in Germany.MethodsWe used routine attendance data from emergency departments, which continuously transferred data between week 10 2017 and 10 2021, with ICD-10 codes available for > 75% of attendances. Case definitions for acute respiratory infection (ARI), severe acute respiratory infection (SARI), influenza-like illness (ILI), respiratory syncytial virus infection (RSV) and COVID-19 were based on a combination of ICD-10 codes, and/or chief complaints, sometimes combined with information on hospitalisation and age.ResultsWe included 1,372,958 attendances from eight emergency departments. The number of attendances dropped in March 2020 during the first COVID-19 pandemic wave, increased during summer, and declined again during the resurge of COVID-19 cases in autumn and winter of 2020/21. A pattern of seasonality of respiratory infections could be observed. By using different case definitions (i.e. for ARI, SARI, ILI, RSV) both the annual influenza seasons in the years 2017-2020 and the dynamics of the COVID-19 pandemic in 2020/21 were apparent. The absence of the 2020/21 influenza season was visible, parallel to the resurge of COVID-19 cases. SARI among ARI cases peaked in April-May 2020 (17%) and November 2020-January 2021 (14%).ConclusionSyndromic surveillance using routine emergency department data can potentially be used to monitor the trends, timing, duration, magnitude and severity of illness caused by respiratory viruses, including both influenza viruses and SARS-CoV-2.

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.

[The different periods of COVID-19 in Germany: a descriptive analysis from January 2020 to February 2021]. / Die verschiedenen Phasen der COVID-19-Pandemie in Deutschland: Eine deskriptive Analyse von Januar 2020 bis Februar 2021.

The first case of coronavirus SARS-CoV­2 infection in Germany was diagnosed on 27 January 2020. To describe the pandemic course in 2020, we regarded four epidemiologically different periods and used data on COVID-19 cases from the mandatory reporting system as well as hospitalized COVID-19 cases with severe acute respiratory infection from the syndromic hospital surveillance.Period 0 covers weeks 5 to 9 of 2020, where mainly sporadic cases of younger age were observed and few regional outbreaks emerged. In total, 167 cases with mostly mild outcomes were reported. Subsequently, the first COVID-19 wave occurred in period 1 (weeks 10 to 20 of 2020) with a total of 175,013 cases throughout Germany. Increasingly, outbreaks in hospitals and nursing homes were registered. Moreover, elderly cases and severe outcomes were observed more frequently. Period 2 (weeks 21 to 39 of 2020) was an interim period with more mild cases, where many cases were younger and often travel-associated. Additionally, larger trans-regional outbreaks in business settings were reported. Among the 111,790 cases, severe outcomes were less frequent than in period 1. In period 3 (week 40 of 2020 to week 8 of 2021), the second COVID-19 wave started and peaked at the end of 2020. With 2,158,013 reported cases and considerably more severe outcomes in all age groups, the second wave was substantially stronger than the first wave.Irrespective of the different periods, more elderly persons and more men were affected by severe outcomes.

[Monitoring of COVID-19 by extending existing surveillance for acute respiratory infections]. / Überwachung von COVID-19 durch Erweiterung der etablierten Surveillance für Atemwegsinfektionen.

As part of the national influenza pandemic preparedness, surveillance systems have been established in Germany in addition to the mandatory notifications according to the Protection Against Infection Act. The aim of these systems is the description, analysis, and evaluation of the epidemiology of acute respiratory infections (ARIs), the identification of the circulating viruses, and the trend. Since the beginning of the COVID-19 pandemic, the systems have been expanded to enable monitoring of infections with SARS-CoV­2.Three systems are presented: GrippeWeb, the primary care sentinel Arbeitsgemeinschaft Influenza with its electronic reporting module SEEDARE, and the ICD-10-based hospital sentinel ICOSARI. With these systems, ARIs can be monitored at the population, outpatient, and inpatient levels. In combination with the monitoring of mortality, these systems provide important information on the frequency of different stages of disease severity in the population. In order to expand the systems to SARS-CoV­2, only a few adjustments were needed.As the case definitions for ARIs were preserved, historical baselines of the systems can still be used for comparison. All systems are structured in such a way that stable and established reference values are available for calculating weekly proportions and rates.This is an important addition to the mandatory reporting system of infectious diseases in Germany, which depends on the particular testing strategy, the number of tests performed, and on specific case definitions, which are adapted as required.The surveillance systems have proven to be feasible and efficient in the COVID-19 pandemic, even when compared internationally.

Influenza-associated pneumonia as reference to assess seriousness of coronavirus disease (COVID-19).

Information on severity of coronavirus disease (COVID-19) (transmissibility, disease seriousness, impact) is crucial for preparation of healthcare sectors. We present a simple approach to assess disease seriousness, creating a reference cohort of pneumonia patients from sentinel hospitals. First comparisons exposed a higher rate of COVID-19 patients requiring ventilation. There were more case fatalities among COVID-19 patients without comorbidities than in the reference cohort. Hospitals should prepare for high utilisation of ventilation and intensive care resources.

Surveillance of COVID-19 school outbreaks, Germany, March to August 2020.

Mitigation of the coronavirus disease (COVID-19) pandemic in Germany included school closures in early March 2020. After reopening in April, preventive measures were taken in schools. We analysed national surveillance system data on COVID-19 school outbreaks during different time periods. After reopening, smaller outbreaks (average: 2.2/week) occurred despite low incidence in the general population. School closures might have a detrimental effect on children and should be applied only cautiously and in combination with other measures.

Zoonotic infection with swine A/H1avN1 influenza virus in a child, Germany, June 2020.

A zoonotic A/sw/H1avN1 1C.2.2 influenza virus infection was detected in a German child that presented with influenza-like illness, including high fever. There was a history of close contact with pigs 3 days before symptom onset. The child recovered within 3 days. No other transmissions were observed. Serological investigations of the virus isolate revealed cross-reactions with ferret antisera against influenza A(H1N1)pdm09 virus, indicating a closer antigenic relationship with A(H1N1)pdm09 than with the former seasonal H1N1 viruses.

First cases of coronavirus disease 2019 (COVID-19) in the WHO European Region, 24 January to 21 February 2020.

In the WHO European Region, COVID-19 surveillance was implemented 27 January 2020. We detail the first European cases. As at 21 February, nine European countries reported 47 cases. Among 38 cases studied, 21 were linked to two clusters in Germany and France, 14 were infected in China. Median case age was 42 years; 25 were male. Late detection of the clusters' index cases delayed isolation of further local cases. As at 5 March, there were 4,250 cases.

Low 2018/19 vaccine effectiveness against influenza A(H3N2) among 15-64-year-olds in Europe: exploration by birth cohort.

IntroductionInfluenza A(H3N2) clades 3C.2a and 3C.3a co-circulated in Europe in 2018/19. Immunological imprinting by first childhood influenza infection may induce future birth cohort differences in vaccine effectiveness (VE).AimThe I-MOVE multicentre primary care test-negative study assessed 2018/19 influenza A(H3N2) VE by age and genetic subgroups to explore VE by birth cohort.MethodsWe measured VE against influenza A(H3N2) and (sub)clades. We stratified VE by usual age groups (0-14, 15-64, ≥ 65-years). To assess the imprint-regulated effect of vaccine (I-REV) hypothesis, we further stratified the middle-aged group, notably including 32-54-year-olds (1964-86) sharing potential childhood imprinting to serine at haemagglutinin position 159.ResultsInfluenza A(H3N2) VE among all ages was -1% (95% confidence interval (CI): -24 to 18) and 46% (95% CI: 8-68), -26% (95% CI: -66 to 4) and 20% (95% CI: -20 to 46) among 0-14, 15-64 and ≥ 65-year-olds, respectively. Among 15-64-year-olds, VE against clades 3C.2a1b and 3C.3a was 15% (95% CI: -34 to 50) and -74% (95% CI: -259 to 16), respectively. VE was -18% (95% CI: -140 to 41), -53% (95% CI: -131 to -2) and -12% (95% CI: -74 to 28) among 15-31-year-olds (1987-2003), 32-54-year-olds (1964-86) and 55-64-year-olds (1954-63), respectively.DiscussionThe lowest 2018/19 influenza A(H3N2) VE was against clade 3C.3a and among those born 1964-86, corresponding to the I-REV hypothesis. The low influenza A(H3N2) VE in 15-64-year-olds and the public health impact of the I-REV hypothesis warrant further study.

[Infectious diseases and their ICD coding : What could be improved by the introduction of ICD-11?] / Infektionskrankheiten und ihre Codierung : Was kann sich durch die ICD-11 verbessern?

The revision of the International Classification of Diseases (ICD) could change morbidity and mortality statistics significantly, which also affects the area of infectious diseases. Infectious diseases are classified according to their etiology, affected body system or the life period during which the episode occurs. Specific challenges arise from emerging pathogens and the respective necessary adaptation. For epidemiologic analysis ICD-10 does not always offer enough additional information.ICD provides the basis for international comparison of infectious disease morbidity and mortality statistics, but it is also used to collect data for surveillance and research purposes, e. g. the notification system for infectious diseases, syndromic surveillance systems and the evaluation of data quality by using secondary data sources.ICD-11 offers the chance to better represent epidemiological concepts of infectious diseases by adding more relevant information as affected body system or manifestation. Due to the complexity of coding, ensuring continuity of morbidity and mortality statistics could be challenging.

Is the impact of childhood influenza vaccination less than expected: a transmission modelling study.

BACKGROUND: To reduce the burden of severe influenza, most industrialized countries target specific risk-groups with influenza vaccines, e.g. the elderly or individuals with comorbidities. Since children are the main spreaders, some countries have recently implemented childhood vaccination programs to reduce overall virus transmission and thereby influenza disease in the whole population. The introduction of childhood vaccination programs was often supported by modelling studies that predicted substantial incidence reductions. We developed a mathematical transmission model to examine the potential impact of childhood influenza vaccination in Germany, while also challenging established modelling assumptions. METHODS: We developed an age-stratified SEIR-type transmission model to reproduce the epidemic influenza seasons between 2003/04 and 2013/14. The model was built upon German population counts, contact patterns, and vaccination history and was fitted to seasonal data on influenza-attributable medically attended acute respiratory infections (I-MAARI) and strain distribution using Bayesian methods. As novelties we (i) implemented a stratified model structure enabling seasonal variability and (ii) deviated from the commonly assumed mass-action-principle by employing a phenomenological transmission rate. RESULTS: According to the model, by vaccinating primarily the elderly over ten seasons 4 million (95% prediction interval: 3.84 - 4.19) I-MAARI were prevented which corresponds to an 8.6% (8.3% - 8.9%) reduction compared to a no-vaccination scenario and a number-needed-to-vaccinate (NNV) to prevent one I-MAARI of 37.1 (35.5 - 38.7). Additional vaccination of 2-10 year-old children at 40% coverage would have led to an overall I-MAARI reduction of 17.8% (17.1 - 18.7%) mostly due to indirect effects with a NNV of 20.7 (19.6 - 21.6). When employing the traditional mass-action-principle, the model predicted a more than 3-fold higher I-MAARI reduction (55.6%) due to childhood vaccination. CONCLUSION: In Germany, the introduction of routine childhood influenza vaccination could considerably reduce I-MAARI among all age-groups and improve the NNV. However, the predicted impact is much lower compared to previous studies, which is primarily caused by our phenomenological approach to modelling influenza virus transmission.

Highly pathogenic avian influenza A(H5N8) outbreaks: protection and management of exposed people in Europe, 2014/15 and 2016.

Introduction of highly pathogenic avian influenza (HPAI) virus A(H5N8) into Europe prompted animal and human health experts to implement protective measures to prevent transmission to humans. We describe the situation in 2016 and list public health measures and recommendations in place. We summarise critical interfaces identified during the A(H5N1) and A(H5N8) outbreaks in 2014/15. Rapid exchange of information between the animal and human health sectors is critical for a timely, effective and efficient response.

[Evaluation of an ICD-10-based electronic surveillance of acute respiratory infections (SEEDARI) in Germany]. / Evaluation einer ICD-10-basierten elektronischen Surveillance akuter respiratorischer Erkrankungen (SEEDARE) in Deutschland.

BACKGROUND: Every year epidemic waves of influenza and other acute respiratory infections (ARIs) cause a highly variable burden of disease in the population. Thus, assessment of the situation and adaptation of prevention strategies have to rely on real time syndromic surveillance. OBJECTIVE: We have established an ICD-10-based electronic system allowing rapid capture and transmission of information on ARI (SEEDARI), in Germany. Here we report the evaluation of this new system based on results of the syndromic and virologic surveillance carried out by the working group on influenza in Germany (AGI). METHODS: Consultations and ICD10-codes (J00-J22, J44.0 and B34.9) between week 16 in 2009, and week 15 in 2013, were used for comparison with AGI data. The time course and the correlation of weekly estimates of the incidence of medically attended ARI (MAARI) and ARI/100 consultations were analyzed for the different surveillance systems. RESULTS: The number of participating medical practices in SEEDARI almost doubled from 2009 (n = 65) to 2013 (n = 111). A total of almost 6.8 million consultations and 465,006 diagnosed ARIs were transmitted. The comparison of weekly estimated incidence of MAARI per 100,000 capita derived from SEEDARI and the results of the AGI showed high statistical correlation (Spearman correlation coefficient rs = 0,924; n = 209; p < 0,001). The proportion of diagnosed influenza (J09-J11) and the weekly positivity rate from virological surveillance during epidemic waves also showed high correlations. DISCUSSION: We conclude that SEEDARI represents a valid system for syndromic influenza surveillance. The case-based ICD-10 approach allows a detailed analysis of the actual situation and also seems suitable for population-based studies.

[Influenza pandemic deaths in Germany from 1918 to 2009. Estimates based on literature and own calculations]. / Todesfälle durch Influenzapandemien in Deutschland 1918 bis 2009. Schätzwerte auf Basis der Literatur und ergänzende eigene Berechnungen.

BACKGROUND AND OBJECTIVE: Estimation of the number of deaths as a consequence of the influenza pandemics in the twentieth and twenty-first centuries (i.e. 1918-1919, 1957-1958, 1968-1970 and 2009) is a challenge worldwide and also in Germany. After conducting a systematic literature search complemented by our own calculations, values and estimates for all four pandemics were collated and evaluated. METHOD: A systematic literature search including the terms death, mortality, pandemic, epidemic, Germany, 1918, 1957, 1968, 2009 was performed. Hits were reviewed by title and abstract and selected for possible relevance. We derived our own estimates using excess mortality calculations, which estimate the mortality exceeding that to be expected. All identified values were evaluated by methodology and quality of the database. Numbers of pandemic deaths were used to calculate case fatality rates and were compared with global values provided by the World Health Organization. RESULTS: For the pandemic 1918-1919 we identified 5 relevant publications, 3 for the pandemics 1957-1958 and 1968-1970 and 3 for 2009. For all four pandemics the most plausible estimations were based on time series analyses, taken either from the literature or from our own calculations based on monthly or weekly all cause death statistics. For the four pandemics these estimates were in chronological order 426,600 (1918-1919), 29,100 (1957-1958), 46,900 (1968-1970) and 350 (2009) excess pandemic-related deaths. This translates to an excess mortality ranging between 691 per 100,000 (0.69 % in 1918-1919) and 0.43 per 100,000 (0.00043 % in 2009). Case fatality rates showed good agreement with global estimates. CONCLUSION: We have proposed plausible estimates of pandemic-related excess number of deaths for the last four pandemics as well as excess mortality in Germany. The heterogeneity among pandemics is large with a variation factor of more than 1000. Possible explanations include characteristics of the virus or host (immunity), social conditions, status of the healthcare system and medical advances.