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Nils Skajaa,1– 4 Lise Gehrt,3,4 Heta Nieminen,5 Ida Laake,6 Hélène Englund,7 Ute Wolff Sönksen,8 Berit Feiring,6 Christine Stabell Benn,3,4,9 Lill Trogstad,6 Arto A Palmu,5 Signe Sørup1,3 1Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark; 2National Institute of Public Health, University of Southern Denmark, Copenhagen, Denmark; 3Research Center for Vitamins and Vaccines, Statens Serum Institut, Copenhagen, Denmark; 4Bandim Health Project, Open Patient Data Explorative Network, Odense University Hospital/Department of Clinical Research, University of Southern Denmark, Odense C, Denmark; 5Department of Public Health and Welfare, Finnish Institute for Health and Welfare, Tampere, Finland; 6Division of Infection Control and Environmental Health, The Norwegian Institute of Public Health, Oslo, Norway; 7Unit for Vaccination Programmes, Public Health Agency of Sweden, Solna, Sweden; 8Reference Laboratory for Antimicrobial Resistance, Infection Preparedness, Statens Serum Institut, Copenhagen, Denmark; 9Danish Institute for Advanced Study, University of Southern Denmark, Odense C, DenmarkCorrespondence: Signe Sørup, Department of Clinical Epidemiology, Aarhus University Hospital, Olof Palmes Allé 43-45, Aarhus N, 8200, Denmark, Email SigneSorup@clin.au.dkObjective: To compare the use of antibiotics in children in four Northern European countries.Methods: We conducted a register-based study based on individual-level prescription data from national prescription registers. We identified all redeemed outpatient prescriptions for systemic antibiotics in children aged 0– 14 years from July 2006 to June 2017 in Denmark, Finland, Norway, and Sweden. We computed incidence rates and incidence rate ratios of treatment episodes with any antibiotic and different antibiotic classes.Results: In 2016/2017, the rates of antibiotic treatment episodes per 1000 person-years in children aged 0– 14 years were 429, 284, 219, and 184 in Finland, Denmark, Sweden, and Norway, respectively, and the rate ratios (95% confidence intervals) compared with Norway were 2.33 (2.33– 2.34), 1.54 (1.54– 1.55), and 1.19 (1.19– 1.20) in Finland, Denmark, and Sweden, respectively. The rate of antibiotic treatment episodes declined over time in all countries. The relative reductions in 2016/2017 compared with 2006/2007 were 36% in Finland, 40% in Denmark, 49% in Sweden, and 29% in Norway. Treatment episodes peaked between age 12 and 18 months. The most used antibiotic class was beta-lactamase sensitive penicillins among all children in Norway and Sweden and among children above two years in Denmark, while penicillins with extended spectrum were most used in Finland and among the youngest children in Denmark.Conclusion: In all countries, the use of antibiotics in children declined between 2006 and 2017. However, there were still considerable differences in antibiotic use between otherwise quite similar Nordic countries, with a more than 2-fold difference between the countries with the lowest and highest rates. Interventions to reduce the number of antibiotic treatment episodes in the countries with higher rates could reduce the total antibiotic use.Keywords: antibiotic use, pediatric, multi-national comparison, antimicrobial consumption, prescription patterns

Lise Gehrt,1,2 Ida Laake,3 Hélène Englund,4 Heta Nieminen,5 Christine Stabell Benn,1,2,6 Berit Feiring,3 Lill Trogstad,3 Arto A Palmu,5 Signe Sørup2,7 1Bandim Health Project, Research Unit Open, Department of Clinical Research, University of Southern Denmark, Odense C, Denmark; 2Research Center for Vitamins and Vaccines, Statens Serum Institut, Copenhagen, Denmark; 3Division of Infection Control, Norwegian Institute of Public Health, Oslo, Norway; 4Unit for Vaccination Programmes, Public Health Agency of Sweden, Solna, Sweden; 5Department of Public Health and Welfare, Finnish Institute for Health and Welfare, Tampere, Finland; 6Danish Institute for Advanced Study, University of Southern Denmark, Odense C, Denmark; 7Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, DenmarkCorrespondence: Lise Gehrt, Bandim Health Project, Research Unit Open, Department of Clinical Research, University of Southern Denmark, Odense C, Denmark, Email lgehrt@health.sdu.dkPurpose: Comparing rates of childhood infectious disease hospitalisations across countries may uncover areas for improvement in the prevention of severe childhood infections. We compared rates of childhood infectious disease hospital contacts across Denmark, Finland, Norway, and Sweden with the overall objective to elucidate potential differences in burden of disease and in organisational and registration practices.Methods: Using national registries, we estimated incidence rates for infectious disease hospital contacts between 2008 and 2017 among children aged 0– 14 years. We investigated the rates for different types of contacts (inpatient or outpatient including emergency room), duration of admission, and by sex.Results: During the study period, the rate of all hospital contacts per 1000 person-years was highest in Sweden (125.2) followed by Finland (87.1), Denmark (79.0), and Norway (62.1). The rates aligned for inpatient contacts with overnight stays; 19.3 (Denmark), 16.6 (Finland), 16.3 (Norway), and 13.0 (Sweden); these were highest in early infancy in all countries. A peak around 1 year of age was seen in all countries except in Sweden. The rates were higher among boys compared with girls in early childhood, after 13 years of age the rates among girls surpassed the boys.Conclusion: Large cross-country differences were observed for outpatient and short-term hospital contacts for infectious diseases, affected by differences in organisational structures and coding practices across and within countries over time. Inpatient contacts requiring overnight stays reflected more comparable levels of severe infections across countries. Childhood infectious disease morbidity was greatest among boys and before 2 years of age.Keywords: infectious disease hospitalisations, paediatric, patient registry, multinational study, Nordic countries

Background: The impact of vaccination on the type and risk of specific post-COVID symptoms after Omicron infection is not clear. We aimed to investigate the excess risk and patterns of 22 symptoms 3-5 months after Omicron infection, comparing uninfected and infected subjects with and without recent booster vaccination., Methods: We conducted a population-based prospective study based on four questionnaire-based cohorts linked to national health registries. Our study includes female and male participants aged 11-80 years from The Norwegian Mother, Father, and Child Cohort Study, The Norwegian Influenza Pregnancy Cohort, The Senior Cohort, and The Young Adult Cohort. All participants registered presence of 22 COVID-related symptoms irrespective of infection and vaccination status., Results: The study sample includes more than 31,000 uninfected and 26,000 Omicron infected subjects. Among infected subjects, 12 % were vaccinated with two doses >130 days before the primary infection (median 154 days) but had not received a third dose, while 76 % had received a third (booster) dose (median 40 days before infection). Among those with two doses only, the excess risk for new symptoms after infection (vs. no infection) were up to 15 % for women and 9 % for men. Among infected subjects with recent booster dose, the corresponding excess risks were 7 % among women and up to 5 % among men. The largest risk differences after recent booster vaccination were seen for poor memory, brain fog, and fatigue. Post-COVID symptoms were more often detected among young and middle-aged adults than among adolescents and older age groups., Conclusion: Recent booster vaccination before infection substantially reduced both neurocognitive and cardiorespiratory symptoms occurring at least 3 months after Omicron infection., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2025 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Objectives: To investigate if receipt of measles-mumps-rubella (MMR) vaccine following the third dose of diphtheria-tetanus-acellular pertussis (DTaP3) is associated with reduced rates of non-targeted infectious disease hospitalisations., Methods: Register based cohort study following 1,397,027 children born in Denmark, Finland, Norway, and Sweden until 2 years of age. Rates of infectious disease hospitalisations with minimum one overnight stay according to time-varying vaccination status were compared using Cox proportional hazards regression analysis with age as the underlying timescale and including multiple covariates. Summary estimates were calculated using random-effects meta-analysis., Results: Compared with DTaP3 and no MMR vaccine, MMR after DTaP3 was associated with reduced rates of infectious disease hospitalisations: aHR was 0.86 (0.83-0.89) in Denmark, 0.70 (0.64-0.75) in Finland, 0.71 (0.68-0.74) in Norway, and 0.71 (0.65-0.77) in Sweden: summary estimate was 0.75 (0.65 to 0.84). A beneficial association was also seen in a negative control exposure analysis (3 vs. 2 DTaP doses): summary estimate aHR was 0.81 (0.75-0.87)., Conclusions: Having MMR as the most recent vaccine was consistently associated with reduced rates of infectious disease hospitalisation. However, bias may account for at least some of the observed association. Randomised controlled trials are warranted to inform the optimal timing of MMR for both its specific and potential non-specific effects., Competing Interests: Declaration of Competing Interest All authors have completed the ICMJE uniform disclosure form at http://www.icmje.org/disclosure-of-interest/http://www.icmje.org/disclosure-of-interest/ and declare: All authors had financial support from NordForsk (grant number: 83839) and LG had financial support from Odense University Hospital Research fund (A-number: 2519) and the faculty scholarship from the University of Southern Denmark for the submitted work; Finnish Institute for Health and Welfare (THL) has conducted Public-Private Partnership with vaccine manufacturers and has received research funding from Sanofi Inc., Pfizer Inc., and GlaxoSmithKline Biologicals SA. HN, ML, and AAP have been investigators in these studies, but they have received no personal remuneration; no other relationships or activities that could appear to have influenced the submitted work. Department of Clinical Epidemiology, Aarhus University and Aarhus University Hospital, receives institutional research funding from public and private entities for studies of medicines and vaccines, to and administered by Aarhus University. None of these are relevant to the current study. SS is a salaried employee of Department of Clinical Epidemiology., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Estimating the trend of new infections was crucial for monitoring risk and for evaluating strategies and interventions during the COVID-19 pandemic. The pandemic revealed the utility of new data sources and highlighted challenges in interpreting surveillance indicators when changes in disease severity, testing practices or reporting occur. Our study aims to estimate the underlying trend in new COVID-19 infections by combining estimates of growth rates from all available surveillance indicators in Norway. We estimated growth rates by using a negative binomial regression method and aligned the growth rates in time to hospital admissions by maximising correlations. Using a meta-analysis framework, we calculated overall growth rates and reproduction numbers including assessments of the heterogeneity between indicators. We find that the estimated growth rates reached a maximum of 25% per day in March 2020, but afterwards they were between -10% and 10% per day. The correlations between the growth rates estimated from different indicators were between 0.5 and 1.0. Growth rates from indicators based on wastewater, panel and cohort data can give up to 14 days earlier signals of trends compared to hospital admissions, while indicators based on positive lab tests can give signals up to 7 days earlier. Combining estimates of growth rates from multiple surveillance indicators provides a useful description of the COVID-19 pandemic in Norway. This is a powerful technique for a holistic understanding of the trends of new COVID-19 infections and the technique can easily be adapted to new data sources and situations., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2025 Rø et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Aim: Estimate the incidence of asthma among children aged 0 to 15 years in Denmark, Finland, Norway and Sweden during 2000-2017., Methods: Cases of preschool asthma (up to 6 years) and school-age asthma (from 6 years) were identified through national registers using an algorithm including hospital diagnoses and prescription medicines. The respective cumulative incidence (CI) was estimated in 1-year age intervals for each country and birth year., Results: The CI of algorithm-based preschool asthma peaked for the birth cohorts 2008 or 2009 at 14.8% in Denmark, 11.0% in Finland, 15.1% in Norway and 13.7% in Sweden. For later birth cohorts, a slight decrease was observed. The CI of school-age asthma was 7.1% in Denmark, 10.5% in Finland, 9.7% in Norway and 10.2% in Sweden (children born in 2002). A slight decline over time was seen in Denmark and Norway, and a slight increase in Sweden and Finland., Conclusion: Finland had a markedly lower CI of preschool asthma and Denmark lower CI of school-age asthma as estimated by prescriptions and hospital diagnoses. Preschool asthma may have plateaued in the Nordic countries. For school-age asthma trends over time varied by country. Differences in diagnostic and prescription practices may have influenced the results., (© 2025 The Author(s). Acta Paediatrica published by John Wiley & Sons Ltd on behalf of Foundation Acta Paediatrica.)

It has been suggested that non-live vaccines may increase susceptibility to non-targeted infections and that such deleterious non-specific effects are more pronounced in girls. We investigated whether receipt of non-live vaccine against human papillomavirus (HPV) was associated with increased risk of infectious disease hospitalization. A nationwide cohort study based on detailed individual-level data from national registries was performed in Denmark, Finland, Norway, and Sweden. The cohort consisted of girls aged 11-14 years in Denmark, Finland, and Norway, and 10-14 years in Sweden. Cox regression, with extensive control for potential confounders, was used to assess whether risk of infectious disease hospitalization with at least one overnight stay differed according to time-varying HPV vaccination status. In total, 754 458 girls were included in the analysis. The infectious disease hospitalization rate (per 10 000 person years) was 44.1 in Denmark, 35.7 in Finland, 37.1 in Norway, and 28.5 in Sweden. Comparing HPV-vaccinated with HPV-unvaccinated person time, the adjusted hazard ratio (95% confidence interval) was 0.81 (0.72, 0.90) in Denmark, 0.69 (0.60, 0.80) in Finland, 0.76 (0.66, 0.88) in Norway, and 0.59 (0.49, 0.71) in Sweden. Decreased risk was observed regardless of number of doses, except in Norway, where risk among girls with only one dose did not differ from risk among unvaccinated girls. Receipt of HPV vaccine was consistently associated with decreased risk of infectious disease hospitalization among girls in the Nordic countries. Our study does not support that HPV vaccines have deleterious non-specific effects., Competing Interests: Declarations. Ethics approval: Ethical approval is not required for registry-based studies in Denmark or Finland. However, the study was approved by the Danish Data Protection Agency and by the Institutional Review Board of the Finnish Institute for Health and Welfare. Study approval was obtained from the Regional Ethics Committee, South-East, in Norway and from the Regional Ethical Review Board, Stockholm, in Sweden. Competing interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: HN and ML are investigators in vaccine-related studies for which the Finnish Institute for Health and Welfare has received funding from GSK, Pfizer and Sanofi Pasteur. Department of Clinical Epidemiology, Aarhus University and Aarhus University Hospital, the employer of SS, receives institutional research funding from public and private entities for studies of medicines and vaccines, to and administered by Aarhus University. None of these are relevant to the current study. The remaining authors report no relation that could be construed as a conflict of interest. Consent to participate: Informed consent was not obtained from the individuals included in the study, as data were obtained from nationwide health registries to which reporting is mandatory., (© 2024. The Author(s).)

Heterogeneity in vaccine response, particularly in vulnerable populations like the elderly, represents a significant public health challenge. We conducted an in-depth examination of immune cell profiles before and after SARS-CoV-2 vaccination utilizing mass cytometry in a cohort of healthy Norwegian seniors (65-80 years). We have demonstrated that higher pre-vaccination frequencies of CD27 + IgD - class-switched memory B cells and subsets of CD27 - CD24 + CD38 + transitional B cells were associated with a robust vaccine response. Post-vaccination, high responders exhibited increased frequencies of IFN-γ + CD4 + T cells with antigen recall and a concurrent decrease in CCR6(+) T H cell subset frequencies compared to low responders. The presence of a γδ T cell subset displaying polyfunctional cytokine responses was also associated with better vaccine response in the elderly. This in-depth profiling sheds light on inherent differences in immune cell frequencies and functions that may offer insights for targeted vaccination strategies in older populations., Competing Interests: Competing interests: The authors declare that no competing interests., (© 2024. The Author(s).)

Background: According to Norwegian registries, 91% of individuals ≥ 16 years had received ≥ 1 dose of COVID-19 vaccine by mid-July 2022, whereas less than 2% of children < 12 years were vaccinated. Confirmed COVID-19 was reported for 27% of the population, but relaxation of testing lead to substantial underreporting. We have characterized the humoral immunity to SARS-CoV-2 in Norway in the late summer of 2022 by estimating the seroprevalence and identifying antibody profiles based on reactivity to Wuhan or Omicron-like viruses in a nationwide cross-sectional collection of residual sera, and validated our findings using cohort sera., Methods: 1,914 anonymized convenience sera and 243 NorFlu-cohort sera previously collected from the Oslo-area with reported infection and vaccination status were analyzed for antibodies against spike, the receptor-binding domain (RBD) of the ancestral Wuhan strain and Omicron BA.2 RBD, and nucleocapsid (N). Samples were also tested for antibodies inhibiting RBD-ACE2 interaction. Neutralization assays were performed on subsets of residual sera against B.1, BA.2, XBB.1.5 and BQ.1.1., Results: The national seroprevalence estimate from vaccination and/or infection was 99.1% (95% CrI 97.0-100.0%) based on Wuhan (spike&#95;W and RBD&#95;W) and RBD&#95;BA2 antibodies. Sera from children < 12 years had 2.2 times higher levels of antibodies against RBD&#95;BA2 than RBD&#95;W and their seroprevalence estimate showed a 14.4 percentage points increase when also including anti-RBD&#95;BA2 antibodies compared to Wuhan-antibodies alone. 50.3% (95% CI 45.0-55.5%) of residual sera from children and 38.1% (95% CI 36.0-40.4%) of all residual sera were positive for anti-N-antibodies. By combining measurements of binding- and ACE2-RBD-interaction-inhibiting antibodies, reactivity profiles indicative of infection and vaccination history were identified and validated using cohort sera. Residual sera with a profile indicative of hybrid immunity were able to neutralize newer Omicron variants XBB.1.5 and BQ.1.1., Conclusions: By late summer of 2022, most of the Norwegian population had antibodies to SARS-CoV-2, and almost all children had been infected. Antibody profiles indicated that children mostly had experienced a primary Omicron infection, while hybrid immunity was common among adults. The finding that sera displaying hybrid immunity could neutralize newer Omicron variants indicates that Wuhan-like priming of the immune response did not have a harmful imprinting effect and that infections induce cross-reacting antibodies against future variants., (© 2024. The Author(s).)

Objective: To predict birth weight at various potential gestational ages of delivery based on data routinely available at the first antenatal visit., Design: Individual participant data meta-analysis., Data Sources: Individual participant data of four cohorts (237 228 pregnancies) from the International Prediction of Pregnancy Complications (IPPIC) network dataset., Eligibility Criteria for Selecting Studies: Studies in the IPPIC network were identified by searching major databases for studies reporting risk factors for adverse pregnancy outcomes, such as pre-eclampsia, fetal growth restriction, and stillbirth, from database inception to August 2019. Data of four IPPIC cohorts (237 228 pregnancies) from the US (National Institute of Child Health and Human Development, 2018; 233 483 pregnancies), UK (Allen et al, 2017; 1045 pregnancies), Norway (STORK Groruddalen research programme, 2010; 823 pregnancies), and Australia (Rumbold et al, 2006; 1877 pregnancies) were included in the development of the model., Results: The IPPIC birth weight model was developed with random intercept regression models with backward elimination for variable selection. Internal-external cross validation was performed to assess the study specific and pooled performance of the model, reported as calibration slope, calibration-in-the-large, and observed versus expected average birth weight ratio. Meta-analysis showed that the apparent performance of the model had good calibration (calibration slope 0.99, 95% confidence interval (CI) 0.88 to 1.10; calibration-in-the-large 44.5 g, -18.4 to 107.3) with an observed versus expected average birth weight ratio of 1.02 (95% CI 0.97 to 1.07). The proportion of variation in birth weight explained by the model (R 2 ) was 46.9% (range 32.7-56.1% in each cohort). On internal-external cross validation, the model showed good calibration and predictive performance when validated in three cohorts with a calibration slope of 0.90 (Allen cohort), 1.04 (STORK Groruddalen cohort), and 1.07 (Rumbold cohort), calibration-in-the-large of -22.3 g (Allen cohort), -33.42 (Rumbold cohort), and 86.4 g (STORK Groruddalen cohort), and observed versus expected ratio of 0.99 (Rumbold cohort), 1.00 (Allen cohort), and 1.03 (STORK Groruddalen cohort); respective pooled estimates were 1.00 (95% CI 0.78 to 1.23; calibration slope), 9.7 g (-154.3 to 173.8; calibration-in-the-large), and 1.00 (0.94 to 1.07; observed v expected ratio). The model predictions were more accurate (smaller mean square error) in the lower end of predicted birth weight, which is important in informing clinical decision making., Conclusions: The IPPIC birth weight model allowed birth weight predictions for a range of possible gestational ages. The model explained about 50% of individual variation in birth weights, was well calibrated (especially in babies at high risk of fetal growth restriction and its complications), and showed promising performance in four different populations included in the individual participant data meta-analysis. Further research to examine the generalisability of performance in other countries, settings, and subgroups is required., Trial Registration: PROSPERO CRD42019135045., Competing Interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/disclosure-of-interest/ and declare: support from the National Institute for Health and Care Research Health Technology Assessment UK programme for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work., (Copyright © Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Objectives: Previous studies have shown that vaccination against measles, mumps, and rubella (MMR) may have beneficial non-specific effects, reducing the risk of infections not targeted by the vaccine. We investigated if MMR vaccine given after the third dose of diphtheria-tetanus-acellular pertussis vaccine (DTaP3), was associated with reduced rates of antibiotic treatments., Methods: Register-based cohort study following children from the age of recommended MMR vaccination until age 2 years. We included 831,287 children born in Denmark, Finland, Norway, and Sweden who had received DTaP3 but not yet MMR vaccine. Cox proportional hazards regression with age as the underlying timescale and vaccination status as a time-varying exposure was used to estimate covariate-adjusted Hazard Ratios (aHRs) and inverse probability of treatment weighted (IPTW) HRs of antibiotic treatments. Summary estimates were calculated using random-effects meta-analysis., Results: Compared with only having received DTaP3, receipt of MMR vaccine after DTaP3 was associated with reduced rates of antibiotic treatments in all countries: the aHR was 0.92 (0.91-0.93) in Denmark, 0.92 (0.90-0.94) in Finland, 0.84 (0.82-0.85) in Norway, and 0.87 (0.85-0.90) in Sweden, yielding a summary estimate of 0.89 (0.85-0.93). A stronger beneficial association was seen in a negative control exposure analysis comparing children vaccinated with DTaP3 vs two doses of DTaP., Conclusions: Across the Nordic countries, receipt of MMR vaccine after DTaP3 was associated with an 11% lower rate of antibiotic treatments. The negative control analysis suggests that the findings are affected by residual confounding. Findings suggest that potential non-specific effects of MMR vaccine are of limited clinical and public health importance for the milder infections treated out-of-hospital in the Nordic setting., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: HN and ML are investigators in vaccine-related studies for which THL has received funding from GSK, Pfizer and Sanofi Pasteur. The remaining authors report no relation that could be construed as a conflict of interest. Department of Clinical Epidemiology, Aarhus University and Aarhus University Hospital, receives institutional research funding from public and private entities for studies of medicines and vaccines, to and administered by Aarhus University. None of these are relevant to the current study. SS is a salaried employee of Department of Clinical Epidemiology., (Copyright © 2024 The Authors. Published by Elsevier India Pvt Ltd. All rights reserved.)

Introduction: SARS-CoV-2 infection causes acute COVID-19 and may result in post-COVID syndrome (PCS). We aimed to investigate how clinicians diagnose PCS and identify associated clinical and demographic characteristics., Methods: We analysed multiregistry data of all SARS-CoV-2 test-positive individuals in Sweden (n=1 057 174) between 1 February 2020 and 25 May 2021. We described clinical characteristics that prompt PCS diagnosis in outpatient and inpatient settings. In total, there were 6389 individuals with a hospital inpatient or outpatient diagnosis for PCS. To understand symptomatology, we examined individuals diagnosed with PCS at least 3 months after COVID-19 onset (n=6389) and assessed factors associated with PCS diagnosis., Results: Mechanical ventilation correlated with PCS (OR 114.7, 95% CI 105.1 to 125.3) compared with no outpatient/inpatient contact during initial COVID-19. Dyspnoea (13.4%), malaise/fatigue (8%) and abnormal pulmonary diagnostic imaging findings (4.3%) were the most common features linked to PCS. We compared clinical features of PCS with matched controls (COVID-19 negative, n=23 795) and COVID-19 severity-matched patients (COVID-19 positive, n=25 556). Hypertension associated with PCS cohort (26.61%) than in COVID-19-negative (OR 17.16, 95% CI 15.23 to 19.3) and COVID-19-positive (OR 9.25, 95% CI 8.41 to 10.16) controls, although most individuals received this diagnosis before COVID-19. Dyspnoea was the second most common feature in the PCS cohort (17.2%), and new to the majority compared with COVID-19-negative (OR 54.16, 95% CI 42.86 to 68.45) and COVID-19-positive (OR 18.7, 95% CI 16.21 to 21.57) controls., Conclusions: Our findings highlight factors Swedish physicians associate with PCS., Competing Interests: None declared., (Copyright © Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY. Published by BMJ.)

Objective: Maternal smoking is associated with as much as a 50% reduced risk of preeclampsia, despite increasing risk of other poor pregnancy outcomes that often co-occur with preeclampsia, such as preterm birth and fetal growth restriction. Researchers have long sought to understand whether this perplexing association is biologically based, or a result of noncausal mechanisms. We examined whether smoking-response genes modify the smoking-preeclampsia association to investigate potential biological explanations., Study Design: We conducted a nested case-control study within the Norwegian Mother, Father and Child Birth Cohort (1999-2008) of 2,596 mother-child dyads. We used family-based log-linear Poisson regression to examine modification of the maternal smoking-preeclampsia relationship by maternal and fetal single nucleotide polymorphisms involved in cellular processes related to components of cigarette smoke ( n  = 1,915 with minor allele frequency ≥10%). We further investigated the influence of smoking cessation during pregnancy., Results: Three polymorphisms showed overall ( p  < 0.001) multiplicative interaction between smoking and maternal genotype. For rs3765692 ( TP73 ) and rs10770343 ( PIK3C2G ), protection associated with smoking was reduced with two maternal copies of the risk allele and was stronger in continuers than quitters (interaction p  = 0.02 for both loci, based on testing 3-level smoking by 3-level genotype). For rs2278361 ( APAF1 ) the inverse smoking-preeclampsia association was eliminated by the presence of a single risk allele, and again the trend was stronger in continuers than in quitters (interaction p  = 0.01)., Conclusion: Evidence for gene-smoking interaction was limited, but differences by smoking cessation warrant further investigation. We demonstrate the potential utility of expanded dyad methods and gene-environment interaction analyses for outcomes with complex relationships between maternal and fetal genotypes and exposures., Key Points: · Maternal and fetal genotype may differentially influence preeclampsia.. · Smoking-related genes did not strongly modify smoking-preeclampsia association.. · Smoking cessation reduced strength of gene by smoking interactions.., Competing Interests: None declared., (Thieme. All rights reserved.)

Objectives: To identify factors associated with change in mental distress at the onset of the COVID-19 pandemic, relative to pre-pandemic levels, and with changes during the following 1.5 years. Methods: The prospective Norwegian Mother, Father and Child Cohort Study collected eight waves of data during the pandemic (March 2020-September 2021) in 105,972 adult participants used for this analyses. A piecewise latent growth model was fitted to identify initial level and longitudinal changes in mental distress. Results: Mental distress peaked at the beginning of the pandemic. Factors associated with initial increases were: medical conditions, living alone, history of psychiatric disorders, lower education, female sex, younger age, and obesity. Being quarantined or infected with SARS-CoV-2 were associated with increasing distress while being vaccinated was associated with reduced mental distress. Conclusion: Having a chronic disease and being quarantined or infected by the SARS-CoV-2 virus were associated with more mental distress during the pandemic. This knowledge is important for planning interventions to support individuals during future pandemics and other societal crises., Competing Interests: Author OA was consultant to the company HealthLytix. The remaining authors declare that they do not have any conflicts of interest., (Copyright © 2023 Lu, Hannigan, Brandlistuen, Nesvåg, Trogstad, Magnus, Unnarsdóttir, Valdimarsdóttir, Andreassen and Ask.)

The association between coronavirus disease 2019 (COVID-19) vaccination and vaginal bleeding among nonmenstruating women is not well studied. The Norwegian Institute of Public Health followed several cohorts throughout the pandemic and early performed a systematic data collection of self-reported unexpected vaginal bleeding in nonmenstruating women. Among 7725 postmenopausal women, 7148 perimenopausal women, and 7052 premenopausal women, 3.3, 14.1, and 13.1% experienced unexpected vaginal bleeding during a period of 8 to 9 months, respectively. In postmenopausal women, the risk of unexpected vaginal bleeding (i.e., postmenopausal bleeding) in the 4 weeks after COVID-19 vaccination was increased two- to threefold, compared to a prevaccination period. The corresponding risk of unexpected vaginal bleeding after vaccination was increased three- to fivefold in both nonmenstruating peri- and premenopausal women. In the premenopausal women, Spikevax was associated with at 32% increased risk as compared to Comirnaty. Our results must be confirmed in future studies.

Background: Little is known regarding the mental health impact of having a significant person (family member and/or close friend) with COVID-19 of different severity., Methods: The study included five prospective cohorts from four countries (Iceland, Norway, Sweden, and the UK) with self-reported data on COVID-19 and symptoms of depression and anxiety during March 2020-March 2022. We calculated prevalence ratios (PR) of depression and anxiety in relation to having a significant person with COVID-19 and performed a longitudinal analysis in the Swedish cohort to describe temporal patterns., Findings: 162,237 and 168,783 individuals were included in the analysis of depression and anxiety, respectively, of whom 24,718 and 27,003 reported a significant person with COVID-19. Overall, the PR was 1.07 (95% CI: 1.05-1.10) for depression and 1.08 (95% CI: 1.03-1.13) for anxiety in relation to having a significant person with COVID-19. The respective PRs for depression and anxiety were 1.15 (95% CI: 1.08-1.23) and 1.24 (95% CI: 1.14-1.34) if the patient was hospitalized, 1.42 (95% CI: 1.27-1.57) and 1.45 (95% CI: 1.31-1.60) if the patient was ICU-admitted, and 1.34 (95% CI: 1.22-1.46) and 1.36 (95% CI: 1.22-1.51) if the patient died. Individuals with a significant person with hospitalized, ICU-admitted, or fatal COVID-19 showed elevated prevalence of depression and anxiety during the entire year after the COVID-19 diagnosis., Interpretation: Family members and close friends of critically ill COVID-19 patients show persistently elevated prevalence of depressive and anxiety symptoms., Funding: This study was primarily supported by NordForsk (COVIDMENT, 105668) and Horizon 2020 (CoMorMent, 847776)., Competing Interests: AL received a grant from the Fredrik and Ingrid Thuring Foundation. DLM is a part-time employee of Optima Partners Ltd. EMF received payment for keynote lecture from Astra Zeneca. HA received a grant from the Research Council of Norway. PFS received a grant from the Swedish Research Council (Vetenskapsrådet, award D0886501) and is a consultant and shareholder Neumora Therapeutics for work not directly related to the topics of this paper. OAA received grants from NordForsk (Grant 105668) and the European Union’s Horizon2020 Research and Innovation Programme (Grant 847776; CoMorMent) for the current project and received grants from NIH NIMH, the Research Council of Norway, the South-East Regional Health Authority, Horizon2020, Stiftelsen Kristian Gerhard Jebsen, consulting fees from Biogen, Cortechs.ai and Milken, payment or honoraria from Janssen, Lundbeck and Sunovion, and reports patent Intranasal Administration, US20160310683 A1, participation on DSMB 21 board as PI, and stock options with Cortechs.ai. UAV received grants from NordForsk (Grants 138929 and 105668). FF received grants from NordForsk, the Swedish Research Council for Health, Working Life and Welfare, the Horizon2020 programme, Swedish Research Council, Swedish Cancer Society, US CDC, US NIH, and the European Research Council. The other authors declare no conflict of interest., (© 2023 The Author(s).)

Background: Many signals of menstrual disturbances as possible side effects of vaccination against COVID-19 have been reported. Our objective was to compare the risk of menstrual disturbances before and after vaccination among women aged 18-30 years in Oslo, Norway., Methods: We used electronic questionnaires to collect reports of menstrual disturbances from 3972 women aged 18-30 years, participating in the population-based Norwegian Young Adult Cohort. We examined the occurrence of menstrual disturbances (heavier bleeding than usual, prolonged bleeding, shorter interval between menstruations, longer interval between menstruations, spot bleedings, stronger pain during menstruation, period pain without bleeding) before and after the first and second dose of COVID-19 vaccine. Relative risks (RR) according to vaccination were estimated using a self-controlled case-series design. We performed additional analyses stratified by vaccine brand, contraception/hormone use, and presence of gynecological condition(s)., Results: The prevalence of any menstrual disturbance was 36.7 % in the last menstrual cycle prior the first vaccine dose. The RR for heavier bleeding than usual was 1.90 (95 % CI: 1.69-2.13) after the first vaccine dose and 1.84 (95 % CI 1.66-2.03) after the second dose. Increased risks of prolonged bleeding, shorter interval between menstruations, and stronger pain during menstruation were also observed after both doses. The RRs did not differ with vaccine brand, contraception/hormone use, or presence of gynecological condition(s) for any of the menstrual disturbances., Conclusion: Menstrual disturbances were common regardless of vaccination. We found increased risk of menstrual disturbances after vaccination, particularly for heavier bleeding than usual, prolonged bleeding, shorter interval between menstruations, and stronger period pain. In the future, menstrual characteristics should be included in vaccine trials., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: Clear evidence of an increased risk for SARS-CoV-2 infection among smokers has not been established. We aimed to investigate associations between cigarette smoking or use of snus (snuff) and other nicotine-containing products and a positive SARS-CoV-2 test, taking test behavior into account., Methods: Current tobacco use and testing behavior during the pandemic were recorded by adult participants from the Norwegian Mother, Father and Child Cohort Study and The Norwegian Influenza Pregnancy Cohort. SARS-CoV-2 infection status was obtained from The Norwegian Surveillance System for Communicable Diseases (MSIS) in May 2021 (n = 78,860) and antibody measurements (n = 5581). We used logistic regression models stratified by gender and adjusted for age, education, region, number of household members, and work situation., Results: Snus use was more common among men (26%) than women (9%) and more prevalent than cigarette smoking. We found no clear associations between cigarette smoking or snus and a COVID-19 diagnosis among men. Associations among women were conflicting, indicating that cigarette smoke was negatively associated with a diagnosis (OR 0.51, 95% CI 0.35, 0.75), while no association was found for snus use (OR 1.07, 95% CI 0.86, 1.34). Compared with non-users of tobacco, both cigarette smokers and snus users had increased odds of being tested for SARS-CoV-2., Conclusions: Cigarette smoking, but not snus use, was negatively associated with SARS-CoV-2 infection in women. The lack of an association between snus use and SARS-CoV-2 infection in this population with prevalent snus use does not support the hypothesis of a protective effect of nicotine., (© 2023. The Author(s).)

Background: Older age is associated with poorer outcomes to COVID-19 infection. The Norwegian Institute of Public Health established a longitudinal cohort of adults aged 65-80 years to study the effects of the COVID-19 pandemic. Here we describe the characteristics of the cohort in general, and specifically the immune responses at baseline and after primary and booster vaccination in a subset of longitudinal blood samples, and the epidemiological factors affecting these responses., Methods: 4551 participants were recruited, with humoral (n=299) and cellular (n=90) responses measured before vaccination and after two and three vaccine doses. Information on general health, infections, and vaccinations were obtained from questionnaires and national health registries., Findings: Half of the participants had a chronic condition. 849 (18·7%) of 4551 were prefrail and 184 (4%) of 4551 were frail. 483 (10·6%) of 4551 had general activity limitations (scored with the Global Activity Limitation Index). After dose two, 295 (98·7%) of 299 participants were seropositive for anti-receptor binding domain IgG, and 210 (100%) of 210 participants after dose three. Spike-specific CD4 and CD8 T cell responses showed high heterogeneity after vaccination and responded to the alpha (B.1.1.7), delta (B.1.617.2), and omicron (B.1.1.529 or BA.1) variants of concern. Cellular responses to seasonal coronaviruses increased after SARS-CoV-2 vaccination. Heterologous prime boosting with mRNA vaccines was associated with the highest antibody (p=0·019) and CD4 T cell responses (p=0·003), and hypertension with lower antibody levels after three doses (p=0·04)., Interpretation: Most older adults, including those with comorbidities, generated good serological and cellular responses after two vaccine doses. Responses further improved after three doses, particularly after heterologous boosting. Vaccination also generated cross-reactive T cells against variants of concern and seasonal coronaviruses. Frailty was not associated with impaired immune responses, but hypertension might indicate reduced responsiveness to vaccines even after three doses. Individual differences identified through longitudinal sampling enables better prediction of the variability of vaccine responses, which can help guide future policy on the need for subsequent doses and their timing., Funding: Norwegian Institute of Public Health, Norwegian Ministry of Health, Research Council of Norway, and Coalition for Epidemic Preparedness Innovations., Competing Interests: Declaration of interests We declare no competing interests., (Copyright © 2023 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license. Published by Elsevier Ltd.. All rights reserved.)

Purpose: The aim of the NONSEnse project is to investigate the non-specific effects of vaccines and immunisation programmes on the overall health of children by using information from the extensive nationwide registers on health and sociodemographic factors in Denmark, Finland, Norway and Sweden., Participants: The cohort covers 9 072 420 children aged 0-17 years, born 1990-2017/2018 and living in Denmark, Finland, Norway or Sweden. All countries use a unique identification number for its permanent residents, which makes it possible to link individual-level information from different registers., Findings to Date: Data collection and harmonisation according to a common data model was completed in March 2022. As a prerequisite for comparing the effects of childhood vaccinations on the overall health of children across the Nordic countries, we have identified indicators measuring similar levels of infectious disease morbidity across these settings. So far, studies pertaining to non-specific effects of vaccines are limited to investigations that could be undertaken using aggregated data sets that were available before the NONSEnse cohort with individual-level information was completely set up., Future Plans: We are currently performing several studies of the effects on non-targeted infectious disease morbidity across the countries following vaccination against measles, mumps, rubella, diphtheria, tetanus, pertussis, human papillomavirus, rotavirus and influenza. Multiple studies are planned within the next years using different study designs to facilitate triangulation of results and enhance causal inference., Registration: No clinical trials will be conducted within the NONSEnse project., Competing Interests: Competing interests: AAP, HN and ML are investigators in vaccine-related studies for which THL has received funding from GSK, Pfizer and Sanofi Pasteur., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Diagnostic assays currently used to monitor the efficacy of COVID-19 vaccines measure levels of antibodies to the receptor-binding domain of ancestral SARS-CoV-2 (RBDwt). However, the predictive value for protection against new variants of concern (VOCs) has not been firmly established. Here, we used bead-based arrays and flow cytometry to measure binding of antibodies to spike proteins and receptor-binding domains (RBDs) from VOCs in 12,000 serum samples. Effects of sera on RBD-ACE2 interactions were measured as a proxy for neutralizing antibodies. The samples were obtained from healthy individuals or patients on immunosuppressive therapy who had received two to four doses of COVID-19 vaccines and from COVID-19 convalescents. The results show that anti-RBDwt titers correlate with the levels of binding- and neutralizing antibodies against the Alpha, Beta, Gamma, Delta, Epsilon and Omicron variants. The benefit of multiplexed analysis lies in the ability to measure a wide range of anti-RBD titers using a single dilution of serum for each assay. The reactivity patterns also yield an internal reference for neutralizing activity and binding antibody units per milliliter (BAU/ml). Results obtained with sera from vaccinated healthy individuals and patients confirmed and extended results from previous studies on time-dependent waning of antibody levels and effects of immunosuppressive agents. We conclude that anti-RBDwt titers correlate with levels of neutralizing antibodies against VOCs and propose that our method may be implemented to enhance the precision and throughput of immunomonitoring., (© 2022. The Author(s).)

Introduction: Maternal cytomegalovirus (CMV) infection in pregnancy may result in vertical transmission of CMV to the child. Long-term effects of congenital CMV infection include visual, cognitive as well as neurological impairment. The aim of this study was to estimate the odds ratios for CMV seropositivity and seroconversion in mothers, with and without delayed language development in 3 year old children, nested within a large cohort., Material and Methods: The Norwegian Mother, Father and Child Cohort Study (MoBa) is a prospective population-based pregnancy cohort that includes 95 200 mothers and 114 500 children. Blood samples were obtained from mothers during pregnancy weeks 17 or 18 in pregnancy and after birth. We included 300 women from MoBa with children suffering from delayed language development at three years of age, based on validated questionnaires. Within the cohort, 1350 randomly selected women were included as controls to perform a nested case-control study. The cases and controls were tested for CMV IgG antibodies by an enzyme-linked immunosorbent assay., Results: Among mothers of cases, 63.2% were CMV-IgG positive in the sample at birth, as compared to 55.9% among controls; OR 1.36, (95% CI; 1.05 to 1.76). Also, among case mothers, 8/118 (6.8%) initially seronegative cases, seroconverted. Among initially seronegative controls, seroconversion occurred in 23/618 (3.7%) mothers. The OR for seroconversion in cases as compared to control mothers was 1.88 (CI; 0.82 to 4.31), thus not statistically significant different., Conclusion: This study shows a higher risk of delayed language development at three years of age in children born by mothers seropositive for CMV, compared to children born from seronegative mothers., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2022 Barlinn et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Background: Understanding how booster vaccination can prevent moderate and severe illness without hospitalization is crucial to evaluate the full advantage of mRNA boosters., Methods: We followed 85 801 participants (aged 31-81 years) in 2 large population-based cohorts during the Omicron BA.1/2 wave. Information on home testing, PCR testing, and symptoms of coronavirus disease 2019 (COVID-19) was extracted from biweekly questionnaires covering the period 12 January 2022 to 7 April 2022. Vaccination status and data on previous SARS-CoV-2 infection were obtained from national registries. Cox regression was used to estimate the effectiveness of booster vaccination compared to receipt of 2-dose primary series >130 days previously., Results: The effectiveness of booster vaccination increased with increasing severity of COVID-19 and decreased with time since booster vaccination. The effectiveness against severe COVID-19 was reduced from 80.9% shortly after booster vaccination to 63.4% in the period >90 days after vaccination. There was hardly any effect against mild COVID-19. The effectiveness tended to be lower among subjects aged ≥60 years than those aged <50 years., Conclusions: This is the first population-based study to evaluate booster effectiveness against self-reported mild, moderate, and severe COVID-19. Our findings contribute valuable information on duration of protection and thus timing of additional booster vaccinations., Competing Interests: Potential conflicts of interests. J. S. has contributed to vaccine effectiveness studies funded by the European Medicines Agency and the European Centre for Disease Prevention and Control. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (© The Author(s) 2022. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)

Background: Whether type-specific human papillomavirus (HPV) infection influences the risk of acquiring infections with other HPV types is unclear. We studied concurrent HPV infections in 17-year-old girls from 2 birth cohorts; the first vaccine-eligible cohort in Norway and a prevaccination cohort., Methods: Urine samples were collected and tested for 37 HPV genotypes. This study was restricted to unvaccinated girls from the prevaccination cohort (n = 5245) and vaccinated girls from the vaccine-eligible cohort (n = 4904). Risk of HPV infection was modelled using mixed-effect logistic regression. Expected frequencies of concurrent infection with each pairwise combination of the vaccine types and high-risk types (6/11/16/18/31/33/35/39/45/51/52/56/58/59) were compared to observed frequencies., Results: Infection with multiple HPV types was more common among unvaccinated girls than vaccinated girls (9.2% vs 3.7%). HPV33 and HPV51 was the only HPV pair that was detected together more often than expected among both unvaccinated (P = .002) and vaccinated girls (P < .001). No HPV pairs were observed significantly less often than expected., Conclusions: HPV33 and HPV51 tended to be involved in coinfection among both unvaccinated and vaccinated girls. The introduction of HPV vaccination does not seem to have had an effect on the tendency of specific HPV types to cluster together., (© The Author(s) 2020. Published by Oxford University Press for the Infectious Diseases Society of America.)

Background: Interventions targeting the same disease but at different points along the disease continuum (e.g., screening and vaccination to prevent cervical cancer [CC]) are often evaluated in isolation, which can affect cost-effectiveness profiles and policy conclusions. We evaluated nonavalent human papillomavirus (HPV) vaccine (9vHPV) compared with bivalent HPV vaccine (2vHPV) alongside deintensified screening intervals for a vaccinated birth cohort to inform a single optimal integrated CC prevention policy., Methods: Using a multimodeling approach, we evaluated the health and economic impacts of alternative CC screening strategies for a Norwegian birth cohort eligible for HPV vaccination in 2021 assuming they received 1) 2vHPV or 2) 9vHPV. We conducted 1) a restricted analysis that evaluated the optimal HPV vaccine under current screening guidelines; and 2) a comprehensive analysis including alternative screening and vaccination strategy combinations. We calculated incremental cost-effectiveness ratios (ICERs) and evaluated them according to different cost-effectiveness thresholds., Results: Assuming a cost-effectiveness threshold of $40,000 per quality-adjusted life year (QALY) gained, we found that, while holding screening intensity fixed, switching the routine vaccination program in Norway from 2vHPV to 9vHPV would not be considered cost-effective (ICER of $132,700 per QALY gained). However, when allowing for varying intensities of CC screening, we found that switching to 9vHPV would be cost-effective compared with 2vHPV under an alternative threshold of $55,000 per QALY gained, if coupled with reductions in the number of lifetime screens., Conclusions: Our analysis highlights the importance of evaluating the full potential policy landscape for country-level decision makers considering policy adoption, including nonindependent primary and secondary prevention efforts, to draw appropriate conclusions and avoid sub-optimal outcomes., Highlights: Without evaluating the full potential policy landscape, including primary and secondary prevention efforts, country-level decision makers may not be able to draw appropriate policy conclusions, resulting in suboptimal outcomes.An applied example from cervical cancer prevention in Norway compared a restricted analysis of current screening guidelines to a comprehensive analysis including alternative screening and vaccination strategy combinations.We found that a switch from bivalent to nonavalent human papillomavirus vaccine would be considered cost-effective in Norway if coupled with reductions in the number of lifetime screens compared with the current screening strategy.A comprehensive analysis that considers how different types of interventions along the disease continuum affect each other will be critical for decision makers interpreting cost-effectiveness analysis results.

The SARS-CoV-2 Omicron variant has more than 15 mutations in the receptor binding domain of the Spike protein enabling increased transmissibility and viral escape from antibodies in vaccinated individuals. It is unclear how vaccine immunity protects against Omicron infection. Here we show that vaccinated participants at a super-spreader event have robust recall response of humoral and pre-existing cellular immunity induced by the vaccines, and an emergent de novo T cell response to non-Spike antigens. Individuals with Omicron SARS-CoV-2 breakthrough infections have significantly increased activated SARS-CoV-2 wild type Spike-specific cytotoxic T cells, activated follicular helper (T FH ) cells, functional T cell responses, boosted humoral responses, and rapid release of Spike and RBD-specific IgG + B cell plasmablasts and memory B cells into circulation. Omicron breakthrough infection affords significantly increased de novo memory T cell responses to non-Spike viral antigens. Concerted T and B cell responses may provide durable and broad immunity., (© 2022. The Author(s).)

Physical, psychological and cognitive symptoms have been reported as post-acute sequelae for COVID-19 patients but are also common in the general uninfected population. We aimed to calculate the excess risk and identify patterns of 22 symptoms up to 12 months after COVID-19. We followed more than 70,000 adult participants in an ongoing cohort study, the Norwegian Mother, Father and Child Cohort Study (MoBa) during the COVID-19 pandemic. Infected and non-infected participants registered presence of 22 different symptoms in March 2021. One year after infection, 13 of 22 symptoms were associated with SARS-CoV-2 infection, based on relative risks between infected and uninfected subjects. For instance, 17.4% of SARS-CoV-2 infected cohort participants reported fatigue that persist 12 months after infection, compared to new occurrence of fatigue that had lasted less than 12 months in 3.8% of non-infected subjects (excess risk 13.6%). The adjusted relative risk for fatigue was 4.8 (95% CI 3.5-6.7). Two main underlying factors explained 50% of the variance in the 13 symptoms. Brain fog, poor memory, dizziness, heart palpitations, and fatigue had high loadings on the first factor, while shortness-of breath and cough had high loadings on the second factor. Lack of taste and smell showed low to moderate correlation to other symptoms. Anxiety, depression and mood swings were not strongly related to COVID-19. Our results suggest that there are clusters of symptoms after COVID-19 due to different mechanisms and question whether it is meaningful to describe long COVID as one syndrome., (© 2022. The Author(s).)

Objectives: To estimate the impact of being laid off from work, having to work from home or having been diagnosed with COVID-19 on self-reported satisfaction with life., Design: Nationwide population-based cohort study., Setting: Norway., Participants: We followed more than 80 000 participants in an ongoing cohort study, the Norwegian Mother, Father and Child Cohort Study (MoBa), during the COVID-19 pandemic. We analysed current life satisfaction in April and again in September/October 2020 for subjects whose work situation and infection status had changed., Main Outcome Measures: Self-reported satisfaction with life, using a scale from 0 (worst) to 10 (best). We analysed the scale both continuously and as a binary variable (

Background: In a previous cohort study of 4-year-old Danish children, revaccination with the live measles-mumps-rubella vaccine (MMR) was associated with a 16% reduction in the rate of hospitalization lasting two days or longer for non-measles-mumps-rubella infections., Aim: To examine if the introduction of revaccination with MMR at 4 years of age in Denmark (spring 2008) and at 7-9 years of age in Sweden (autumn 2009), at a time when there was virtually no measles, mumps or rubella cases, was associated with a reduction in the rate of hospitalization-for-infection lasting two days or longer at the population level., Methods: We included 4-year-olds in Denmark and 7-9-year-olds in Sweden. We obtained the number of hospitalization-for-infection lasting two days or longer from nationwide hospital registers. Person-years at risk were approximated from population statistics for each season and year. We performed an interrupted time series analysis using Poisson regression to estimate the change in hospitalization incidence rates following the introduction of MMR revaccination, adjusting for seasonality. We also performed analyses with control series (3-year-olds in Denmark and 4-year-olds in Sweden)., Results: Comparing the incidence of hospitalization-for-infection lasting two days or longer after the introduction of MMR revaccination with the expected level without an introduction of MMR revaccination resulted in an incidence rate ratio of 1.07 (95% confidence interval [CI] = 0.89-1.28) for 4-year-olds in Denmark and 0.89 (95% CI = 0.77-1.02) for 7-9-year-olds in Sweden in analyses without controls. Analyses with controls gave similar results., Conclusion: This population-level study of the introduction of MMR revaccination in Denmark and Sweden had inadequate power to confirm or refute the findings from an individual-level Danish study of an association between MMR revaccination and a lower incidence rate of hospitalization-for-infection lasting two days or longer., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: HN is an employee of the Finnish Institute for Health and Welfare, which has received research funding from GlaxoSmithKline, Sanofi-Pasteur and Pfizer for clinical trials. All other authors report no conflicts of interest., (Copyright © 2021 The Authors. Published by Elsevier Ltd.. All rights reserved.)