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Background Studies have reported an increased risk for asthma following lower respiratory tract infections, but few studies have specifically assessed this risk in children diagnosed with pneumonia in infancy. Furthermore, it is not fully understood whether this association is indicative of a causal relationship or if certain children have a predisposition for both diseases. Research Question Are children diagnosed with pneumonia in infancy at increased risk for asthma, and what is the role of familial confounding and pneumococcal conjugate vaccine immunization on the association? Study Design and Methods This study was a nationwide register-based cohort analysis of > 900,000 Swedish children to assess the association between pneumonia in infancy and prevalent asthma at 4 years. A secondary aim was to assess if the association has changed after the introduction of nationwide pneumococcal conjugate vaccine (PCV) immunization as this has led to a shift in pneumonia etiology. The study controlled for important confounders, including shared environmental and familial confounding, by using sibling analyses. Results There was a strong association between pneumonia diagnosis in infancy and prevalent asthma at 4 years (adjusted OR, 3.38; 95% CI, 3.26-3.51), as well as in the full sibling analyses (adjusted OR, 2.81; 95% CI, 2.58-3.06). The risk for asthma following pneumonia diagnosis in infancy was slightly higher for those born in the PCV period compared with the pre-PCV period (adjusted OR, 3.80 [95% CI, 3.41-4.24] vs 3.28 [95% CI, 3.15-3.42]) when the proportion of viral pneumonia etiology was also higher (14.5% vs 10.7%, respectively) and the overall asthma prevalence was lower (5.3% vs 6.6%). Interpretation Children diagnosed with pneumonia in infancy have a highly increased risk for prevalent asthma at 4 years, which might have implications for future asthma preventive measures and needs to be considered when assessing the morbidity that can be attributed to pneumonia.

Previous studies have reported a reduction in pediatric emergency visits for communicable diseases during the COVID-19 pandemic, which has been related to the use of face masks and school closures. As Sweden imposed less strict restrictions as compared to most countries we aimed to assess the effect of the behavioral changes, however without school closures and general usage of face masks in the society, on the spread of communicable diseases in children. We calculated cumulative incidences of pediatric emergency visits for lower respiratory tract infections (LRTIs), gastroenteritis and as a control diagnosis urinary tract infections (UTIs) comparing 2020 with 2018-2019. Our results suggests that the behavioral changes including improved basal hygiene routines and physical distancing, had a major impact on the disease transmission of LRTIs (cumulative incidence 0.24% in 2020 versus 0.57% during 2018-2019, p

(1) Immunization with pneumococcal conjugate vaccines has decreased the burden of community-acquired pneumonia (CAP) in children and likely led to a shift in CAP etiology. (2) The Trial of Respiratory infections in children for ENhanced Diagnostics (TREND) enrolled children 1-59 months with clinical CAP according to the World Health Organization (WHO) criteria at Sachs’ Children and Youth Hospital, Stockholm, Sweden. Children with rhonchi and indrawing underwent “bronchodilator challenge”. C-reactive protein and nasopharyngeal PCR detecting 20 respiratory pathogens, were collected from all children. Etiology was defined according to an a priori defined algorithm based on microbiological, biochemical, and radiological findings. (3) Of 327 enrolled children, 107 (32%) required hospitalization, 91 (28%) received antibiotic treatment, 77 (24%) had a chest X-ray performed, and 60 (18%) responded to bronchodilator challenge. 243 (74%) episodes were classified as viral, 11 (3%) as mixed viral-bacterial, five (2%) as bacterial, two (0.6%) as atypical bacterial and 66 (20%) as undetermined etiology. After exclusion of children responding to bronchodilator challenge, the proportion of bacterial and mixed viral-bacterial etiology was 1% and 4%, respectively. (4) The novel TREND etiology algorithm classified the majority of clinical CAP episodes as of viral etiology, whereas bacterial etiology was uncommon. Defining CAP in children &lt, 5 years is challenging, and the WHO definition of clinical CAP is not suitable for use in children immunized with pneumococcal conjugate vaccines.

To assess the clinical effect of empirical treatment with narrow-spectrum ß-lactam monotherapy (NSBM) versus broad-spectrum ß-lactam monotherapy (BSBM) in non-severe community-acquired pneumonia (CAP).Hospitalized patients ≥18 years with CAP who received initial NSBM or BSBM, with a severity score according to CRB-65≤2 (C=confusion, R=respiratory rate30/min, B=systolic blood pressure90 mmHg or diastolic blood pressure ≤60 mmHg, 65= ≥65 years), in the Swedish Pneumonia Register from 2008 to 2011 were included. Primary outcome was 30-day mortality. Secondary outcomes were 90-day mortality, treatment at intensive care unit (ICU), and length of stay (LOS). Propensity score matching was performed to account for differences in baseline characteristics.There were 5961 patients with CRB-65≤1 and 1344 patients with CRB-65=2. In the propensity score matched cohorts the 30-day mortality was 40/1827 (2.2%) with NSBM and 56/1827 (3.1%) with BSBM in CRB-65≤1, and 57/524 (10.9%) and 51/524 (9.7%), respectively, in CRB-65=2. No significant differences in 30-day mortality were observed between NSBM and BSBM in patients with CRB-65≤1 or CRB-65=2, OR 1.41 (95% CI 0.94-2.14) and 0.88 (95% CI 0.59-1.32), respectively. There was no significant difference in 90-day mortality. Patients who received BSBM were more often treated at ICU and had longer LOS.Empirical NSBM appears to be effective in the majority of hospitalized immunocompetent adults with non-severe CAP and should be further evaluated in randomized trials.

Background Previous studies have suggested an association between season of birth and risk of childhood asthma and allergic disease. The association may be modified by birth year and region, or mediated by respiratory tract infections. Objective We aimed to estimate the association between season of birth and risk of childhood asthma/wheeze or allergic rhinoconjunctivitis in a population-based setting, and the mediating effect of lower respiratory infections. Methods Two population-based cohorts were identified from the nationwide Swedish Medical Birth, Patient and Prescribed Drug Registers. The association between birth month/season and asthma/wheeze incidence was analysed using Cox proportional regression in the younger cohort born 2005-2010 (n = 582 494) and asthma/allergic rhinoconjunctivitis prevalence during the 7th year of life using log-binomial models in the older cohort born 2001-2004 (n = 367 583). Interactions were formally tested. Mediation analyses to address the effect of lower respiratory infections were performed in the older cohort using the R package "medflex." Results Children born during fall and winter had an increased risk of asthma/wheeze after 2 years of age in the younger cohort: hazard ratio 1.24 (95% confidence interval, CI 1.17, 1.33) for winter and risk of prevalent asthma during their 7th year of life in the older cohort; prevalence ratio (PR) 1.12 (95% CI 1.08, 1.16) for winter. These estimates were partly mediated by lower respiratory infections; the indirect effect for winter compared with summer was PR 1.03 (95% CI 1.03, 1.04). The association was similar for allergic rhinoconjunctivitis in the 7th year of life, but not mediated by respiratory infections. Conclusion We found that the association between season of birth and risk of childhood asthma/wheeze, but not allergic rhinoconjunctivitis, is partly mediated through lower respiratory infections. Clinical relevance This has important implications for patient care, such as asthma management programmes to notify timing of seasonality for viral respiratory tract infections.

Objective Febrile neutropenia is common in children undergoing chemotherapy for the treatment of malignancies. In the majority of cases, the cause of the fever is unknown. Although respiratory viruses are commonly associated with this condition, the etiologic significance of this finding remains unclear and is therefore the subject of this study. Study design Nasopharyngeal aspirates were collected during 87 episodes of febrile neutropenia in children age 0-18 years, being treated at a children's oncology unit between January 2013 and June 2014. Real-time polymerase chain reaction was used to determine the presence of 16 respiratory viruses. Follow-up samples were collected from children who tested positive for one or more respiratory viruses. Rhinoviruses were genotyped by VP4/VP2 sequencing. Fisher's exact test and Mann-Whitney U test were used for group comparisons. Results At least one respiratory virus was detected in samples from 39 of 87 episodes of febrile neutropenia (45%), with rhinoviruses the most frequently detected. Follow-up samples were collected after a median of 28 days (range, 9-74 days) in 32 of the 39 virus-positive episodes. The respiratory viral infection had resolved in 25 episodes (78%). The same virus was detected at follow-up in one coronavirus and six rhinovirus episodes. Genotyping revealed a different rhinovirus species in two of the six rhinovirus infections. Conclusion The frequency of respiratory viral infections in this group of patients suggests an etiologic role in febrile neutropenia. However, these findings must be confirmed in larger patient cohorts.

Background Community-acquired pneumonia (CAP) is the leading cause of death in children worldwide and a substantial proportion of childhood CAP is caused by viruses. A better understanding of the role of virus infections in this condition is needed to improve clinical management and preventive measures. The aim of the study was therefore to assess the association between specific respiratory viruses and childhood CAP. Methods A case–control study was conducted during 3 years in Stockholm, Sweden. Cases were children aged ≤5 years with radiological CAP. Healthy controls were consecutively enrolled at child health units during routine visits and matched to cases on age and calendar time. Nasopharyngeal aspirates were obtained and analysed by real-time PCR for 15 viruses. Multivariate conditional logistic regression was used to account for coinfections with other viruses and baseline characteristics. Results A total of 121 cases, of which 93 cases met the WHO criteria for radiological pneumonia, and 240 controls were included in the study. Viruses were detected in 81% of the cases (n=98) and 56% of the controls (n=134). Influenza virus, metapneumovirus and respiratory syncytial virus were detected in 60% of cases and were significantly associated with CAP with ORs >10. There was no association with parainfluenza virus, human enterovirus or rhinovirus and coronavirus and bocavirus were negatively associated with CAP. Conclusions Our study indicates viral CAP is an underestimated disease and points out hMPV as a new important target for the prevention of childhood CAP.

BACKGROUND: The swine-origin influenza A(H1N1)pdm09 pandemic of 2009 had a slower spread in Europe than expected. The human rhinovirus (HRV) has been suggested to have delayed the pandemic through viral interference. The importance of co-infections over time during the pandemic and in terms of severity of the disease needs to be assessed. OBJECTIVE: The aim of this study was to investigate respiratory viruses and specifically the presence of co-infections with influenza A(H1N1)pdm09 (H1N1) in hospitalized children during the H1N1 pandemic. A secondary aim was to investigate if co-infections were associated with severity of disease. METHODS: A retrospective study was performed on 502 children with influenza-like illness admitted to inpatient care at a pediatric hospital in Stockholm, Sweden during the 6 months spanning the H1N1 pandemic in 2009. Respiratory samples were analyzed for a panel of 16 viruses by real-time polymerase chain reaction. RESULTS: One or more viruses were detected in 61.6% of the samples. Of these, 85.4% were single infections and 14.6% co-infections (2-4 viruses). The number of co-infections increased throughout the study period. H1N1 was found in 83 (16.5%) children and of these 12 (14.5%) were co-infections. HRV and H1N1 circulated to a large extent at the same time and 6.0% of the H1N1-positive children were also positive for HRV. There was no correlation between co-infections and severity of disease in children with H1N1. CONCLUSIONS: Viral co-infections were relatively common in H1N1 infected hospitalized children and need to be considered when estimating morbidity attributed to H1N1. Population-based longitudinal studies with repeated sampling are needed to improve the understanding of the importance of co-infections and viral interference.