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Postacute symptoms are not uncommon after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection with pre-Omicron variants. How the Omicron variant and coronavirus disease 2019 (COVID-19) booster vaccination influence the risk of postacute symptoms is less clear. We analyzed data from a nationwide Danish questionnaire study, EFTER-COVID, comprising 36 109 individuals aged ≥15 years who were tested between July 2021 and January 2022, to evaluate the associations of the Omicron variant and COVID-19 booster vaccination with postacute symptoms and new-onset general health problems 4 months after infection with SARS-CoV-2. Risk differences (RDs) were estimated by comparing Omicron cases with controls, comparing Omicron cases with Delta cases, and comparing Omicron cases vaccinated with 3 doses with those vaccinated with 2 doses, adjusting for age, sex, body mass index, self-reported chronic diseases, Charlson comorbidity index, health-care occupation, and vaccination status. Four months after testing for SARS-CoV-2 during the Omicron period, cases experienced substantial postacute symptoms and new-onset health problems in comparison with controls; the largest RD was observed for memory issues (RD = 7.4%; 95% CI, 6.4-8.3). However, risks were generally lower than those in the Delta period, particularly for dysosmia (RD = -15.0%; 95% CI, -17.0 to -13.2) and dysgeusia (RD = -11.2%; 95% CI, -13.2 to -9.5). Booster vaccination was associated with fewer postacute symptoms and new-onset health problems 4 months after Omicron infection as compared with 2 doses of COVID-19 vaccine., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health.)

Background and Aims: To demonstrate that administration of 7500 Trichuris suis ova every second week over 24 weeks would reduce the intestinal inflammation in moderate ulcerative colitis., Methods: A single-centre, randomized, double-blinded, placebo-controlled, phase 2b clinical trial of 7500 Trichuris suis ova every two weeks for 24 weeks compared to placebo in moderate activity of ulcerative colitis (Mayo score 6-10) were performed. Primary outcome: Clinical remission. Secondary outcomes: Clinical response at 24 weeks, complete corticosteroid-free clinical remission, endoscopic remission, symptomatic remission at 12 and 24 weeks and partial Mayo score over time., Results: 119 patients were randomized to Trichuris suis ova (n=60) and placebo (n=59). At week 24, clinical remission was achieved in 30% of Trichuris suis ova-treated vs. 34% of placebo-treated (RR=0.89; CI:0.52-1.50; p=0.80, ITT). No difference was found in clinical response in any of the clinical response subgroups. However, in patients who did not need treatment with corticosteroids during the trial, a temporary effect of TSO was seen in the analysis of symptomatic remission of week 12 (p=0.01), and the partial Mayo score at week 14 and week 18 (p<0.05 and p=0.02)., Conclusions: Compared to placebo, Trichuris suis ova was not superior in achieving clinical remission at week 24 in ulcerative colitis or in achieving clinical Mayo score reduction, complete corticosteroid-free clinical remission or endoscopic remission. However, Trichuris suis ova treatment induced symptomatic temporary remission at week 12., (© The Author(s) 2024. Published by Oxford University Press on behalf of European Crohn’s and Colitis Organisation. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Few studies have addressed the possible association between age at menarche and multiple sclerosis (MS), and results are conflicting. We studied this issue in a large prospective cohort study. The study cohort comprised 77,330 women included in the Danish National Birth Cohort (1996-2002). Information on menarcheal age was ascertained at the first interview, which took place in the 16th week of pregnancy. Women were followed for MS from the first interview to December 31, 2011. Associations between age at menarche and risk of MS were evaluated with hazard ratios and 95% confidence intervals using Cox proportional hazards regression models. Overall, 226 women developed MS during an average follow-up period of 11.7 years. Age at menarche among women with MS was generally lower than that among women without MS (Wilcoxon rank-sum test; P = 0.002). We observed an inverse association between age at menarche and MS risk. For each 1-year increase in age at menarche, risk of MS was reduced by 13% (hazard ratio = 0.87, 95% confidence interval: 0.79, 0.96). Early age at menarche appears to be associated with an increased risk of MS. The mechanisms behind this association remain to be established., (© The Author 2017. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: Because parvovirus B19 infection in pregnancy has been associated with infant morbidity and mortality in case reports and after intrauterine transfusion, we tested the population-based association using serum and hospital data of high quality., Methods: We established a cohort of 113 228 children born to women tested for parvovirus B19 infection during pregnancy in a major diagnostic laboratory in Denmark, from 1994 to 2009. Information on 20 selected morbidity diagnoses and on mortality was obtained from the Danish National Patient Register, the Danish Cancer Register and the Danish Civil Registration System. Incidence rate ratios (IRR) were estimated by log-linear Poisson regression with adjustment for age and sex of the child, maternal age and year of maternal parvovirus B19 test., Results: A total of 1095 (1.0%) children were born to mothers who were infected with parvovirus B19 during pregnancy. During 1 million person-years of follow-up, 10 856 children experienced morbidity and 590 children died. Overall, maternal infection status was neither associated with morbidity during infancy (IRR 0.64; 95% CI: 0.40 to 1.02) or childhood (IRR 0.93; 95% CI: 0.77 to 1.14), nor with infant mortality (IRR 0.98; 95% CI: 0.44 to 2.20). Specifically, there was no association with 19 of 20 morbidities. An excess risk of cancer in the central nervous system was observed (IRR 5.88; 95% CI: 1.41 to 24.6); however, the number of exposed cases was very small (n = 2)., Conclusions: Parvovirus B19 infection during pregnancy was not associated with overall morbidity or mortality in infancy and childhood.

In a national cohort comprising 1.5 million Danes born from 1966 to 1992, we studied the association between childhood socioeconomic status (SES) and the risk of multiple sclerosis (MS) from 1981 to 2007 using information about household income and parental educational levels at the person's 15th birthday. The association between childhood SES and MS was evaluated using MS incidence rate ratios with 95% confidence intervals obtained in log-linear Poisson regression analyses. We found no strong association between childhood SES and MS but did observe a tendency toward a reduced risk of MS among children from households with more highly educated parents, particularly mothers. Children whose mothers had a secondary (rate ratio = 0.95, 95% confidence interval: 0.86, 1.04) or higher (rate ratio = 0.86, 95% confidence interval: 0.76, 0.97) education had reduced risks of MS (5% and 14%, respectively) compared with children of mothers with a basic education (P for trend = 0.02). Results were practically unchanged in an analysis restricted to persons aged 15-29 years, among whom the possible effect of own SES on MS risk is considered limited. Overall, SES in childhood seems of no major importance for the subsequent risk of MS; however, offspring of well-educated mothers may be at a slightly reduced risk of MS.

Because parvovirus B19 infection during pregnancy has been associated with increased risk of fetal loss in small or selected study populations, the authors evaluated the risk in a population-based study. A nested case-control study was conducted by using a population-based screening for syphilis in 3 regions in Denmark from 1992 to 1994. Cases of women with fetal loss were identified in the National Patient Register (n = 2,918), and control women with live-born children were identified in the Medical Birth Register (n = 8,429) by matching on age and sampling week. First-trimester serum samples were tested for parvovirus B19 immunoglobulin M positivity. Parvovirus B19 immunoglobulin M positivity was associated with a 71% increased risk of fetal loss (odds ratio = 1.71, 95% confidence interval: 1.02, 2.86). Adjustment for number of children or stratifying for gestational age at loss did not change the risk estimate. Assuming causality, only 0.1% of fetal losses were attributable to parvovirus B19 positivity, a proportion which could increase to approximately 1% during epidemic periods. In conclusion, acute parvovirus B19 infection during the first trimester of pregnancy was associated with an increased risk of fetal loss. However, the impact on the overall burden of fetal losses appeared small even during epidemics.

Background: Intestinal bacteria have been implicated in the etiology of the common inflammatory bowel diseases (IBD) ulcerative colitis and Crohn's disease. Because delivery by cesarean section disturbs the normal bacterial colonization of the newborn's intestine, we determined the risk of IBD according to mode of delivery., Methods: A register-based national cohort study of 2.1 million Danes born 1973-2008. The effect of mode of delivery on IBD incidence in the age-span 0-35 years was estimated by means of confounder-adjusted incidence rate ratios (IRRs) with 95% confidence intervals (CIs) obtained in Poisson regression analysis. Information on mode of delivery was obtained from the Danish Medical Birth Registry and cases of IBD were identified in the Danish National Patient Registry 1977-2008., Results: During 32.6 million person-years of follow-up, a total of 8142 persons were diagnosed with IBD before age 36 years. Cesarean section was associated with moderately, yet significantly, increased risk of IBD at age 0-14 years (IRR 1.29, 95% CI 1.11-1.49), regardless of parental disposition to IBD. Assuming causality, an estimated 3.2% of IBD cases before age 15 years were attributable to cesarean section., Conclusions: Rates of IBD with onset in childhood are moderately increased after birth by cesarean section but underlying mechanisms remain unclear. Even if the association is causal, the possible impact of increasing cesarean section practices on the overall burden of IBD in childhood is small., (Copyright © 2011 Crohn's & Colitis Foundation of America, Inc.)

Background: An individual's intestinal bacterial flora is established soon after birth. Delivery by Cesarean section (c-section) deprives the newborn of colonization with maternal vaginal bacteria. We determined whether delivery by c-section is associated with an altered risk of infection with intestinal bacterial pathogens., Methods: In a cohort of 1.7 million Danes born 1973-2005 we identified cases of laboratory-confirmed non-typhoidal Salmonella species, Campylobacter species, Yersinia enterocolitica, Shigella species, and Shiga toxin-producing Escherichia coli from 1991-2005 in the National Registry of Enteric Pathogens. Using Poisson-regression we estimated confounder-adjusted incidence rate ratios (IRRs) for infection according to mode of delivery., Results: During 14.0 million person-years of follow-up, 22,486 individuals were diagnosed with 1 intestinal bacterial infection. C-section was associated with a small increase in risk at age 1 to <2 years (IRR, 1.09; 95% confidence interval, 1.00-1.18) and at age 2 to <5 years (IRR, 1.08; 95% confidence interval, 1.00-1.17), but after age 5 years, there was no significant association. Assuming causality only 0.62% of intestinal bacterial infections were attributable to c-section., Conclusions: Mode of delivery appears not to be a clinically relevant determinant of risk for intestinal bacterial infections. The possible impact of increasing frequencies of c-section on the overall burden of intestinal bacterial infections appears negligible.

It has been hypothesized that age at infection with a common microbial agent may be associated with the risk of multiple sclerosis (MS). The authors addressed this hypothesis by using number of older siblings and other sibship characteristics as an approximation of age at exposure to common infections. Data on family characteristics and vital status from the Danish Civil Registration System were used to establish a cohort of all Danes whose mothers had been born in Denmark since 1935. Persons diagnosed with MS during the period 1968-1998 were identified through linkage with the Danish Multiple Sclerosis Register. The cohort of 1.9 million Danes was followed for 28.1 million person-years; during that time, 1,036 persons developed MS. Overall, there was no association between number of older siblings, number of younger siblings, total number of siblings, age distance from the nearest younger sibling, or exposure to younger siblings under 2 years of age and risk of MS later in life. There was no association of MS risk with multiple birth (vs. singleton birth) or with the age of the mother or father at birth. These results do not lend support to the hypothesis that number of older siblings or any of the other sibship characteristics studied is associated with risk of MS.

Multiple sclerosis has been hypothesized to be the result from an aberrant immune response possibly triggered by delayed exposure to a common childhood infection. Because the vast majority of previous studies testing this hypothesis have been based on a history of childhood infections recalled years to decades later in adulthood, we investigated whether age at six common childhood infections was associated with risk of multiple sclerosis, using information recalled in the childhood of a historical cohort of school children in Denmark. Cases included all individuals with multiple sclerosis in the country born between 1940 and 1975, who had attended school in the capital, Copenhagen. Controls were age- and sex-matched peers. School health records were obtained for all subjects. The records contained information on measles, pertussis, scarlet fever, birth order, sibship size, social class of the father, school years, and name of school and attended school classes for children born since 1940 (n(cases) = 455, n(controls) = 1801). For children born since 1950, the records also contained information on rubella, varicella and mumps (n(cases) = 182, n(controls) = 690). Neither age at infection with measles, rubella, varicella, mumps, pertussis and scarlet fever (upper age limit, 14 years) nor the cumulative number of these infections between the ages of 10 and 14 years was associated with the risk of multiple sclerosis. In addition, the risk of multiple sclerosis was not associated with birth order or social class. No clustering of multiple sclerosis in school classes was observed. Our findings suggest that measles, rubella, mumps, varicella, pertussis and scarlet fever, even if acquired late in childhood, are not associated with increased risk of multiple sclerosis later in life.