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Aim: The pneumococcal conjugate vaccine, which covered seven serotypes of Streptococcus pneumoniae (PCV7), was introduced in Stockholm, Sweden, in 2007. It was replaced by a 13‐valent vaccine (PCV13) in 2011. We previously reported a decreased incidence of pneumonia and sinusitis among young children 4 years after the introduction of the PCV7. This study followed the incidence of pneumonia, sinusitis, mastoiditis and meningitis for four more years. Methods: We studied validated hospital registry data covering children up to 17 years of age, who were hospitalised in the Stockholm region from 2003 to 2016, when the child population peaked at 485 687. All 11 115 cases diagnosed with pneumonia, coded as bacterial pneumonia, sinusitis, mastoiditis, bacterial meningitis or empyema, were identified. The controls had viral pneumonia or pyelonephritis. Results: The incidence rates for children under 2 years of age hospitalised for sinusitis, mastoiditis and meningitis decreased significantly by 61%–79% during the eight‐year post‐vaccination period. Hospitalisations for bacterial pneumonia decreased by 19%–25% in the same age group. These changes were probably due to both the vaccines and changes in diagnosis routines. Conclusion: The effect of vaccination on children under 2 years of age was sustained 8 years after the introduction of the pneumococcal conjugate vaccines. [ABSTRACT FROM AUTHOR]

Aim: Human bocavirus 1 (HBoV1) has been associated with respiratory tract infections in children. We aimed at retrospectively describing patient characteristics, seasonality, pre‐existing medical conditions, codetections, clinical manifestations and complications of HBoV1 infection in relation to viral load in the child population in Stockholm, with the overarching aim of elucidating the clinical significance of HBoV1. Methods: We included all hospitalised children 0—17 years testing positive for HBoV1 by real‐time polymerase chain reaction on nasopharyngeal aspirates 1 July 2008—30 June 2019. Patients with HBoV1 single detection, high viral load expressed as an HBoV1‐DNA cycle threshold (Ct) < 25, or both, were separately analysed. We retrieved information on pre‐existing conditions and clinical course from the medical records. Results: We found 768 episodes in 727 children, 496 (64.6%) male and 441 (60.7%) previously healthy. The median age was 17.6 months. Most (476/768, 62.0%) episodes occurred during December–March. HBoV1 was in 549 episodes (71.5%) codetected with other viruses. Ct < 25 was independently associated with young age, single detection of HBoV1 and presentation early in the epidemic season. We saw few differences in clinical manifestations between the subgroups. Conclusion: Our findings are consistent with primary HBoV1 infection causing mild‐to‐severe respiratory tract manifestations in young children. [ABSTRACT FROM AUTHOR]

Background: Vaccination against rotavirus was offered in Stockholm to children born on 1 March 2014 and onwards with 85% coverage after two years. We investigated changes in nosocomial diarrhoea 2010—2018 in children admitted to Astrid Lindgren Children's Hospital, Stockholm, Sweden. Methods: We retrospectively identified cases from diagnostic and virology department registers. Complications and chronic medical conditions were retrieved from the case records. Children <18 years of age who developed diarrhoea ≥48 h after admission for another diagnosis and had a faecal sample submitted to the virology department were included. Results: There were 474 episodes of nosocomial diarrhoea. Of these, 401 (85%) occurred in children with chronic medical conditions. In children <5 years the rates of nosocomial rotavirus gastroenteritis, with 95% confidence intervals, significantly decreased from 0.34 (0.25—0.45) per 100 admissions prevaccination to 0.09 (0.04—0.17) postvaccination and from 0,66 (0.48—0.88) to 0.16 (0.07—0.30) cases per 1000 hospital days. Postvaccination norovirus became the most frequent pathogen. Virus-positive cases were more common in young children and in winter months. Conclusions: Before the initiation of rotavirus vaccination, norovirus and rotavirus were equally common causes of nosocomial diarrhoea. Postvaccination, rotavirus was reduced by approximately 75% while the frequency of other viruses did not change. [ABSTRACT FROM AUTHOR]

In Stockholm, Sweden, rotavirus vaccination was offered to children born after 1 March 2014. Our aim was to describe rates of hospitalisation due to community-acquired gastroenteritis before and after the introduction of the vaccine, and aetiology, underlying medical conditions and complications in admitted children. We retrospectively included patients from our catchment area hospitalised with a diagnosis of gastroenteritis during ten infection seasons 2008/2009–2017/2018, whereof six seasons prevaccination and four seasons postvaccination. We studied virus detection data and the patients' medical records. We included 3718 episodes in 3513 children. In 2967 (80%), stools were tested with virus isolation, ELISA, PCR, or bacterial culture; 479 (16%) tested negative. The incidence rates, with 95% confidence intervals, for children <5 years hospitalised for rotavirus gastroenteritis were 2.9 (2.8–3.1) per 1000 person-years prevaccination and 0.65 (0.56–0.74) postvaccination, for a rate ratio (RR) of 0.22 (0.19–0.26, p <.001). The rates for all-cause gastroenteritis were 5.6 (5.4–5.9) prevaccination and 2.5 (2.3–2.7) postvaccination, RR 0.45 (0.42–0.50, p <.001). In 5–17-year-old children norovirus dominated with little change over time. Of patients <5 years, those with underlying conditions constituted a larger proportion postvaccination than prevaccination (30.7% vs. 24.2%, p <.001). A complication other than dehydration, most commonly seizures, arose in 8.8% of the patients <5 years prevaccination and 11.4% postvaccination (p <.05). Rotavirus vaccination reduced the number of children <5 years requiring hospital care for gastroenteritis. We saw no replacement of rotavirus by other viruses. [ABSTRACT FROM AUTHOR]

Aim: Since the introduction in 1979 of rapid testing using immunofluorescence, we have collected information about children hospitalised for confirmed respiratory syncytial virus (RSV) infection in the northern Stockholm area. We here report hospitalisation rates, risk factors and complications in 2008‐2016 compared with 1986‐1998. Methods: Microbiological laboratory reports and retrospective chart review. Comparison of the two periods was complicated by changing testing routines, with a more sensitive method and increased testing of older children in the late period. Results: In infants, there was an 12.3% increase in the population‐based rate of hospital admission for RSV infection from 12.2 to 13.7/1000. Including all children <5 years, there was a 48% increase from 2.7 to 4.0/1000. The median length of stay remained unchanged at 3 days. The need of intensive care decreased in healthy infants but remained high in older children with comorbidity. Conclusion: Considering the changed diagnosis routines, we believe that the rate of hospital admission of infants for RSV infection was unchanged throughout the observed years. The increased rates of older children with confirmed RSV likely resulted from increased testing of children with risk factors for a complicated course. [ABSTRACT FROM AUTHOR]

We aimed to identify hospitalizations due to infectious diseases among asylum seekers and compare them to those of the resident population 1.6.2015–31.10.2016. Administrative numbers assigned to hospitalized non-resident children made them identifiable in the discharge register. The examined populations, expressed as person-years, were 334,573 residents and 7565 asylum seekers. There were 2500 episodes of infectious disease in 2240 resident children and 139 episodes in 121 asylum seekers. Among prevalent infections contracted before or during migration, there were 33 cases of tuberculosis, four of malaria, and one of louse-borne relapsing fever, all of which occurred in 13–17-year-old unaccompanied minors. Among younger asylum seekers, there were no significant differences in the spectrum of infectious discharge diagnoses compared to residents, but across all incident infections, 0–6-year-old asylum seekers had 3.2-fold and 7–12-year-old a 4.7-fold greater risk of being admitted. Screening for multidrug-resistant bacteria showed that 45/160 (28%) of the asylum seekers were colonized, but clinical infections caused by these species were rare. Conclusion: There was a high rate of hospitalizations for acute infectious diseases in asylum-seeking children, but the spectrum and severity of infections were similar to that in resident children. What is known: • Mental and physical health problems are common in immigrant children and adolescents. What is new: • Hospitalizations due to acute infections in asylum-seeking children and adolescents are common. In the context of this study, the severity and spectrum of infectious diseases seemed to be the same in the two groups; the increased hospitalization rate in asylum seekers may be due to social factors and perceived need for more support. [ABSTRACT FROM AUTHOR]

Aim: Children with osteomyelitis present with a range of signs and symptoms and with varying degree of severity. The purpose of this study was to provide data on a population‐based 10‐year material of children with acute osteomyelitis. Methods: All children, 0–14 years in Stockholm Region with acute osteomyelitis hospitalised in July 2005–June 2015, were retrospectively studied. Time to hospital presentation, disease localization, inflammation markers, imaging procedures, microbiology, severity classified by the presence of complications, surgical procedures, hospital length of stay and seasonal variation were recorded. Results: There were 430 children with acute osteomyelitis; 61% were boys. The incidence per 100 000 person‐years was 11.6; 9.3 in girls and 13.1 in boys. Median age at admission was 2.9 years with no peak later in childhood. Median time from first symptom to diagnosis was 4 days (range 1–21) and 48% of the cases were localised to femur or tibia. Mean C‐reactive protein was 59 mg/L (range 1–376). Blood (n = 82) or tissue cultures (n = 54) were positive in 118 (28%) children. The most common pathogen was Staphylococcus aureus (n = 88) followed by Streptococcus pyogenes (n = 12). Surgery was performed in 71 children (17%). There was no mortality. Severe complications were seen in 14 (3.3%) children, five of whom were admitted to intensive care. Median hospital length of stay was 4 days (range 1–60). Conclusions: Osteomyelitis in children is a diagnostic challenge with a low yield of positive bacterial cultures. Few children with uncomplicated disease need surgery, but the risk of severe complications is not negligible. [ABSTRACT FROM AUTHOR]

Aim: We present our results using interferon-gamma release assays in any child <18 years or tuberculin skin tests in Bacille Calmette-Guérin unvaccinated children for tuberculosis contact investigation in Stockholm, Sweden.Methods: During 2000-2019, we investigated 892 children with a median age of seven years. We explored associations between TB infection and characteristics such as closeness to contact, age, sex, BCG status and foreign origin.Results: The overall rates were for TB infection 10.2% (n = 91) and for TB disease 1.1% (n = 10). In addition to infectiousness of index case and closeness of contact, foreign background, male sex and increasing age were independently associated with infection. In foreign-born children, the rates of tuberculosis infection and disease were 18.7% and 3.9%, respectively. In 18/46 (39%) infected foreign-born children, a baseline negative tuberculosis test supported a diagnosis of recent infection.Conclusion: Foreign background, older age and male sex were associated with infection. In a significant proportion of infected children, a previous negative test made recent infection likely. [ABSTRACT FROM AUTHOR]

Aim: This study described the epidemiology and clinical features of childhood tuberculosis (TB) in Stockholm over a 45-year period, when there was a resurge of tuberculosis concomitant with increased immigration.Methods: We describe 220 children up to the age of 16 years with active TB, seen at the Astrid Lindgren Children's Hospital from 1971 to 2015. The study period was divided into three 15-year periods.Results: Cases increased from ten children in 1971-1985 to 76 in 1986-2000 and 134 in 2001-2015, with overall incidence increasing from <1 to four per 100 000. From 2001 to 2015, 79% of cases, or at least one parent, were born in high-incidence countries. The incidence in this group was 35 per 100 000, but remained at 0.9 per 100 000 in other children. After 2000, most cases were detected by active contact tracing and immigrant screening. The most common manifestation was from the lungs. Meningitis and miliary tuberculosis were found in 7%, with two deaths. Antimicrobial resistance was an increasing problem.Conclusion: The increasing incidence of TB in Stockholm was largely limited to children with a background in high-incidence countries. Most children today have subclinical forms of TB. Although preventive measures are effective, severe cases still occur, especially among adolescent immigrants. [ABSTRACT FROM AUTHOR]

Background Influenza remains a common reason for the hospitalization of children. There is a need for long term studies that are also population based. We describe the epidemiology of severe influenza in a defined population 1998–2014. Method Retrospective study of annually collected data of virologically confirmed influenza in hospitalized children 0–17 years living in the catchment area (230,000 children). We gathered information about comorbidity and complications from case records, and compared Influenza A, B and A(H1N1)pdm09 with respect to these factors. Results A total of 922 children with influenza were hospitalized. The mean rate remained unchanged at 22.5–24.2 per 100,000 children per year. There were two major outbreaks: influenza A(H3N2) in 2003–2004 and the A(H1N1) pandemic in 2009–2010. The proportion of children with influenza B increased from 8% during the first half of the study period to 28% during the second half. The highest admission rate was found in children <3 months of age, 169 per 100,000. Children with influenza B were older than those with influenza A. Comorbidity was found in 34%, complications in 41%, and 11% needed intensive care management. The mortality rate was 0.17/100,000 children. Conclusion Influenza remains an important reason for the hospitalization of children, especially during the first years of life. The increasing proportion of influenza B may have to be considered when recommending influenza vaccines. [ABSTRACT FROM AUTHOR]

Background Immunological studies have indicated that the effectiveness of AS03 adjuvanted monovalent influenza A(H1N1)pdm09 vaccine (Pandemrix ® ) may be of longer duration than what is seen for non-adjuvanted seasonal influenza vaccines. Sixty-nine percent of children 6 months–18 years of age in Stockholm County received at least one dose of Pandemrix ® during the 2009 pandemic. We studied the effectiveness of the vaccine during the influenza seasons 2010–2011 and 2012–2013 in children hospitalized with virologically confirmed influenza. The season 2011–2012 was not included, since influenza A(H3N2) was the predominant circulating strain. Methods In a retrospective case-control study using a modified test-negative design we compared the percentage vaccinated with Pandemrix ® among children diagnosed with influenza A(H1N1)pdm09 (cases), with that of those diagnosed with influenza A(H3N2) or influenza B (controls) during the two seasons. We excluded children born after July 1, 2009, since only children who were 6 months of age or older received the pandemic vaccine in October–December 2009. Results During the 2010–2011 season, 3/16 (19%) of children diagnosed with influenza A(H1N1)pdm09, vs. 32/41 (78%) of those with influenza A(H3N2) or influenza B had been vaccinated with Pandemrix ® in 2009. The odds ratio, after adjustment for sex, age and underlying diseases, for becoming a case when vaccinated with Pandemrix ® was 0.083 (95%CI 0.014, 0.36), corresponding to a VE of 91.7%. During the season 2012–2013, there was no difference between the two groups; 59% of children diagnosed with influenza A(H3N2)/B and 60% of those with influenza A(H1N1)pdm09 had been vaccinated with Pandemrix ® in 2009. Conclusion The AS03 adjuvanted monovalent influenza A(H1N1) pdm09 vaccine (Pandemrix ® ) was effective in preventing hospital admission for influenza A(H1N1)pdm09 in children during at least two seasons. [ABSTRACT FROM AUTHOR]

In January 2006, an after-school carer in Stockholm was diagnosed with open pulmonary tuberculosis (TB) after having been symptomatic for 3 months. The aim of this paper is to illustrate the difficulties encountered in estimating recent transmission of TB among children in an immigrant school population. A tuberculin skin test was performed on 261 pupils aged 6-15 y and an additional interferon-gamma release assay was performed on 20 children. In total, 76% of the children were born in Sweden; however, 95% of the parents originated from countries with TB incidence >25/100,000. Three active TB cases were identified, 1 of whom was culture-positive with the same strain as the index case. Latent tuberculous infection (LTBI) was diagnosed in 35 children. However, the increased risk of earlier infection in this population makes it difficult to evaluate when transmission occurred. The magnitude of recent transmission from the index case will thus be uncertain and indications to treat less clear. [ABSTRACT FROM AUTHOR]

There are few population-based studies of complications due to acute rhinosinusitis in children. The aim was to clarify the admission and complication rate and analyze bacterial cultures in children five to 18 years old in Stockholm, Sweden. This was a population-based observational cohort study with retrospectively collected data from individual medical records, from 1 July 2003 to 30 June 2016 in Stockholm, Sweden. Hospital admissions of children with a discharge diagnosis of rhinosinusitis and related complications were reviewed. Incidence of admission due to acute rhinosinusitis was 7.8 per 100 000 children per year (boys 9.2, girls 6.2) and 61% of the admitted children were boys. A severe – postseptal orbital, intracranial or osseous – complication, was present in 34% of admissions (postseptal orbital 28%, intracranial 6%, osseous 4%), resulting in an incidence of 2.6 severe complications per 100 000 children per year (boys 3.6, girls 1.6). Orbital preseptal cellulitis was present in 88% of admissions. Incidence of surgery was 1.3 per 100 000 per year (boys 1.8, girls 0.8) and the percentage of admitted children that had surgery increased with age. S. pyogenes was the most common pathogen found in the whole cohort (29 admissions), while S. milleri was the most common pathogen found among the children with severe complication and surgery. There is a relative high risk of severe complications in children between five to 18 years that are admitted due to acute rhinosinusitis. There is a need for prospective studies to further analyze the pathogens involved in complications due to acute rhinosinusitis. [ABSTRACT FROM AUTHOR]