The pneumococcal conjugate vaccine had a sustained effect on Swedish children 8 years after its introduction

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.

Pre-admission virus detection during the COVID-19 pandemic in children with and without symptoms of infection

AIM

Pre-admission viral screening is used only in exceptional situations such as pandemics. We therefore evaluated pre-admission screening for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), respiratory syncytial virus (RSV) and influenza during the COVID-19 pandemic, comparing epidemiology and clinical features of admitted children.

METHODS

Children were screened at a paediatric emergency department from 1 March 2020 to 30 June 2022 by nasopharyngeal sampling and polymerase chain reaction kit. We retrospectively retrieved positive results from the laboratory and scrutinised charts of admitted children.

RESULTS

Out of 15 927 screened children, 522, 127 and 572 were positive and admitted with RSV, influenza A or SARS-CoV-2, respectively. Of these, 29 (5.6%), 26 (24.1%) and 245 (44.8%) were incidental findings, lacking symptoms of infection. RSV and influenza A were initially absent but re-emerged in the autumn of 2021. The rate of COVID-19 rose when the Omicron variant emerged in December 2021. The median age of children with RSV was 0.3 years, of those with influenza A 6.7 years and of those with COVID-19 1.6 years. Major complications were rare.

CONCLUSION

Frequent incidental detections of SARS-CoV-2 likely reflected widespread presence of a mild infection. Clinically, COVID-19 was like other viral respiratory infections in children.

Seizures in hospitalised paediatric patients with SARS-CoV-2 and comparison of severity with seizures in hospitalised paediatric patients with other respiratory viruses during the COVID-19 pandemic: a population-based cohort study

OBJECTIVE

To study seizures in patients hospitalised due to SARS-CoV-2 infection, and compare their severity with seizures in patients hospitalised due to other viral respiratory tract infections (RTIs).

DESIGN

Observational population-based cohort study.

SETTING

Northern Stockholm.

PATIENTS

Patients aged 1 month-18 years hospitalised due to SARS-CoV-2 with and without seizures, and patients of the same age hospitalised due to other viral RTIs with seizures, between 1 March 2020 and 30 June 2022.

MAIN OUTCOME MEASURES

The prevalence of seizures in hospitalised patients due to SARS-CoV-2, the evaluation of assumed predictors of seizures and the comparison of severity markers in patients with SARS-CoV-2 versus other RTIs.

RESULTS

32 of 239 included patients (13.4%) admitted due to SARS-CoV-2 infection had seizures. Central nervous system (CNS) disease and the omicron period had significantly increased OR for seizures (OR: 5.12; CI: 2.06 to 12.72 and OR: 3.01; CI: 1.15 to 7.88, respectively). Seizures in patients with SARS-CoV-2 were more common in children older than 5 years (p=0.001), even in the absence of fever (p=0.007), as compared with other viral RTIs. The duration of hospitalisation was longer in patients with seizures due to other viral RTIs (p=0.023). There was no significant difference regarding severity markers of seizures between the two groups.

CONCLUSIONS

CNS disease and the omicron period were risk factors for seizures in patients with SARS-CoV-2, who were older than patients with other RTIs. The severity of seizures was comparable between the two groups; hospitalisation was however longer in patients with other RTIs.

Reduction of rotavirus as a cause of nosocomial diarrhoea in northern Stockholm after introducing the rotavirus vaccine

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.

Human bocavirus 1 epidemiology in children in relation to virus load and codetection

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.

A Swedish population-based study of complications due to acute rhinosinusitis in children 5-18 years old

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

All-cause gastroenteritis hospitalisations of children decreased after the introduction of rotavirus vaccine in Stockholm

BACKGROUND

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

Rotavirus vaccination reduced the number of children <5 years requiring hospital care for gastroenteritis. We saw no replacement of rotavirus by other viruses.

Children hospitalised with four common viral diseases showed epidemiological differences but few socio-economic variations

AIM

This study explored the differences in demographic and socio-economic factors between children hospitalised due to four common viral infections.

METHODS

Demographic data were obtained from Statistics Sweden on >3000 children admitted to Astrid Lindgren Children's Hospital in 2009-2014 with rotavirus, influenza, respiratory syncytial virus (RSV) or chickenpox. We compared demographic and socio-economic factors between case groups using logistic regression with rotavirus cases as reference.

RESULTS

There were differences in the median age at admission; RSV cases were younger (0.4 years), influenza (2.4 years) and chickenpox cases (2.7 years) older than rotavirus cases (1.2 years). RSV, influenza and chickenpox cases lived in families with more children than rotavirus cases. RSV and influenza cases were more likely to have underlying chronic conditions. Mothers of RSV cases were more likely to be born in Sweden. Further socio-economic differences were not robustly confirmed in sensitivity analyses.

CONCLUSION

We found a few differences in demographic factors between children hospitalised with the four common infections, which were mainly explained by the epidemiology and transmission patterns of these infections.

Rates and risk factors of severe respiratory syncytial virus infection in 2008-2016 compared with 1986-1998

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.

Acute infection as cause of hospitalization of asylum-seeking children and adolescents in Stockholm, Sweden 2015-2016

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.

A 10-year retrospective survey of acute childhood osteomyelitis in Stockholm, Sweden

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.

Foreign background and older age of children were associated with infection in Swedish tuberculosis contacts

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.

Serious complications due to acute rhinosinusitis in children up to five years old in Stockholm, Sweden - Still a challenge in the pneumococcal conjugate vaccine era

OBJECTIVES

The aim of this study was to analyze the rate of admissions, the rate of serious complications (postseptal orbital complications and surgery) and the bacterial etiology of acute rhinosinusitis in hospitalized children under five years old in Stockholm County, eight years after the introduction of the pneumococcal conjugate vaccine (PCV). The secondary aim was to compare this period with the period four years prior to the vaccine's introduction.

METHODS

This was a population-based, descriptive observational study with retrospectively collected data from 1 July 2008 to 30 June 2016 in Stockholm County. Hospital admissions of children with a discharge diagnosis of rhinosinusitis and related complications were reviewed and compared to the pre-PCV period of 2003-2007.

RESULTS

A total of 215 children were admitted, for a yearly incidence of 18.8 per 100 000 children (22.8 for boys, 14.6 for girls). Computer tomography-verified postseptal orbital complications occurred in 29 cases (13.5%) and surgery was necessary in nine (4.2%). Pathogens other than Streptococcus pneumoniae were found in the cases with postseptal complication or surgery (Streptococcus pyogenes in four, Haemophilus influenzae in three and Staphylococcus aureus in one case). In comparison to the four years pre-PCV, the incidence of admission decreased from 43.81 to 20.31 and 17.45 per 100 000/year for the two four-year periods after vaccine introduction. The incidence of CT-verified postseptal complication increased slightly from 1.51 to 2.34 and 2.74 per 100 000/year. The incidence of surgeries increased marginally but continued to be very low, from 0.22 to 0.54 and 1.03 per 100 000/year.

CONCLUSIONS

Complications due to acute rhinosinusitis in children living in Stockholm County continues to be very rare after the introduction of pneumococcal vaccine. Hospitalization has decreased for children under five years old after PCV introduction, but the incidence or postseptal complications and surgery in the same population increased slightly. Predominantly bacteria other than Streptococcus pneumoniae was found. There is a need of larger studies to determine trends, and a need of prospective studies to elucidate the bacterial etiology, of serious complications due to acute rhinosinusitis in children.

Effective Tuberculosis Contact Investigation Using Interferon-Gamma Release Assays

During 2000 to 2018, 1831 children were screened as part of tuberculosis contact investigation at the Stockholm Northern Clinic. The risk of a child having a positive tuberculin skin test was 33% and positive interferon-gamma release assay 12%. The risk of tuberculosis disease was 6.1% (tuberculin skin test) and 13% (interferon-gamma release assay) in positive-testing children.

Impact on affected families and society of severe rotavirus infections in Swedish children assessed in a prospective cohort study

BACKGROUND

Few prospective cohort studies have estimated the overall impact of severe rotavirus gastroenteritis (RVGE) leading to hospitalization on families and society. We assessed human and economic resources needed to care for an affected average child aged <5 years in Sweden.

METHODS

The study was conducted in Astrid Lindgren Children's Hospital which serves approximately 14% of all Swedish children <5 years of age. All children admitted with acute gastroenteritis in the study period were tested for rotavirus. Health care consumption was collected prospectively and publically available unit costs used to calculate direct costs. Non-medical and indirect costs were collected in interviews with families using a standardized questionnaire during the hospital stay and approximately 14 days post-discharge.

RESULTS

144/206 children (70%) with laboratory-confirmed RVGE were included. The median age was 14 months. The average total cost per hospitalized child was €3894, of which €2169 (56%) was due to direct healthcare-related costs (including Emergency Department visits and in-patient care), €104 (2%) to non-medical direct costs and €1621 (42%) to indirect costs due to productivity loss. Carers of children with severe RVGE were absent from work on average five days per study child: four days during hospitalization of affected child and one day due to gastroenteritis in the carer.

CONCLUSIONS

Costs for RVGE are dominated by direct costs which are similar to some other countries in Europe, but indirect costs due to productivity loss are also important, and should be considered in decisions to introduce rotavirus vaccines into national vaccination programmes.

Changing diagnosis coding routines may confound the results of longitudinal childhood pneumonia studies

AIM

This Swedish study compared the discharge diagnosis codes used for children up to the age of five hospitalised for acute lower respiratory tract infections before and after the introduction of the pneumococcal conjugate vaccine in 2007.

METHODS

The International Classification of Diseases-10th revision codes were used. We compared the discharge diagnosis codes at the Astrid Lindgren Children's Hospital from 1 July 2005 to 30 June 2007 (n=1,127) and 1 July 2011 to 30 June 2013 (n=1,240) in relation to the diagnostic methods used.

RESULTS

There was a 54% reduction in the rate of all-cause pneumonia from the first to the second period in children aged 0-1 years, but some of this could have been due to the improved diagnosis of viral infections and us changing the code for respiratory syncytial virus infection from pneumonia to bronchiolitis. The overall rate of acute lower respiratory tract infections was unchanged.

CONCLUSION

We could not determine how much of the reduction in bacterial pneumonia in children under one was because of the introduction of the pneumococcal conjugate vaccine, based solely on discharge codes. Longitudinal register studies should take changes in diagnosis codes into account.

Review of the aetiology, diagnostics and outcomes of childhood encephalitis from 1970 to 2009

AIM

Encephalitis is a rare, serious condition, and antiviral therapies, increased knowledge of inflammatory pathways and improved diagnostics have increased the therapeutic possibilities. We describe 40 years of childhood encephalitis in Sweden, covering the diagnostics, aetiology and outcomes.

METHODS

We reviewed the clinical data that were available for all children discharged from the Karolinska University Hospital in Stockholm following treatment for encephalitis from 1970 to 2009. The hospital treated all children in the region with the condition during the study period.

RESULTS

There were 408 episodes of encephalitis from 1970 to 2009 and the incidence was similar over the whole period, ranging from 6.4 to 8.7 per 100 000 child years. Although mortality markedly decreased from 10% in the first decade to zero in the last decade, and aetiologies shifted, no clear long-term improvements in outcome were seen. The need for intensive care was unchanged (18-20%) for each of the study intervals, possibly indicating that the severity of cases remained unaltered.

CONCLUSION

Understanding the pathophysiological mechanisms of encephalitis is vitally important for developing more efficient treatment regimens. As well as reporting the results of this 40-year study, this study considers possible explanations, addresses current therapeutic options and explores directions for central nervous system infection research.

Tuberculosis infection and disease in the 2015 cohort of unaccompanied minors seeking asylum in Northern Stockholm, Sweden

BACKGROUND

Minors with a stated age <18 years unaccompanied by a responsible adult form an increasing part of refugees to Europe. They are older than other asylum-seeking children and many come from countries with a high tuberculosis (TB) incidence. During the 2015 refugee crisis, 35,369 of 162,877 refugees (22%) seeking asylum in Sweden were unaccompanied minors, which gave us the opportunity to study their burden of TB infection and disease.

METHODS

Of the unaccompanied minors seeking asylum in Sweden during 2015, 2936 (8.3%) were allocated to northern Stockholm. Of these, 2422 were from countries with an incidence of TB exceeding 100/10⁵, and were screened for TB infection with a Mantoux tuberculin skin test or a QuantiFERON-TB Gold®. Those from countries with a lower TB incidence were screened only if they had other risk factors for TB exposure.

RESULTS

Of those screened, 349 had a positive test and were referred to the northern paediatric TB clinic at Astrid Lindgren Children's Hospital. Of these, 16 had TB disease and 278 latent tuberculosis infection (LTBI), while we considered 53 uninfected. In addition, eight sought medical attention with symptomatic TB outside the screening system. Cohort rates were 6.8% of LTBI and 0.5% of TB in minors from Afghanistan and 26-32% of LTBI and 3.4-3.5% of TB among those from Eritrea, Ethiopia or Somalia.

CONCLUSION

We conclude that TB infection and disease is common among asylum-seeking unaccompanied minors, especially among those from the Horn of Africa.

[The child immunisation programme--effective but insufficient. Experiences from the Astrid Lindgren pediatric hospital, 2008–2013]

The national Swedish immunisation programme includes vaccine against diphtheria, tetanus, polio, pertussis, Haemophilus influenzae type B, Pneumococcus as well as measles, mumps and rubella. Data were collected on hospital admissions for children 0- 17 years of age of vaccine-preventable diseases during 2008-2013 at Astrid Lindgren Children's Hospital, Stockholm. Patients were identified by discharge diagnosis codes as well as from the clinical microbiology laboratory. There were rare cases of measles and mumps, and only a few cases of invasive bacterial diseases. The dominating pathogens were influenza A and B, rotavirus and varicella zoster virus. Our national programme is effective, but vaccine preventable infections still cause significant morbidity in young children. An extended vaccine programme might significantly reduce the need of hospitalisations.

The impact of pneumococcal conjugate vaccine on community-acquired pneumonia hospitalizations in children with comorbidity

The burden of community-acquired pneumonia (CAP) in high-income countries is still significant. The introduction of pneumococcal conjugate vaccines (PCV) has reduced the overall need for hospitalization for CAP. However, it is not clear whether children with underlying disease also have benefitted from the PCV immunization programme. Children 0 to <5 years of age hospitalized with CAP and discharged with an ICD-10 code of J13-J18.9 between November 1, 2005, and April 30, 2007 (pre-vaccination period), and November 1, 2010, and April 30, 2012 (post-vaccination period), were eligible for this study. Data on hospitalization and discharge diagnoses were retrieved from the Hospital Registry. In addition, chart review was performed in 50% of the patients. Our result confirmed a decrease in hospitalization rate for CAP in the PCV13 period. Chart review revealed that half of the patients had underlying comorbidity and these children had more severe symptoms and required longer hospital stay. Intensive care was provided to less than 10% of the children and mostly for children with an underlying neurological disease.

CONCLUSIONS

We show that all children have benefitted from the reduction of CAP hospitalization after introduction of PCV. Our finding emphasizes the importance of children with chronic diseases receiving adequate vaccinations that may protect from lower respiratory diseases. What is known? • Community-acquired pneumonia is a leading infectious cause of hospitalizations and death among children <5 years of age globally • Pneumococcal conjugate vaccine reduces the hospitalizations of all-cause pneumonia What is new? • We show that also children with underlying comorbidities have benefitted from PCV immunization with a reduction of CAP hospitalization • We show that approximately half of all children hospitalized with CAP also have underlying comorbidities.

Paediatric tuberculosis cases increased in Stockholm from 1971 to 2015 following the rising number of children with immigrant backgrounds

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.

Interferon-gamma release assays can effectively screen migrants for the tuberculosis infection, but urgent, active cases need clinical recognition

AIM

Increasing numbers of migrants to Sweden are screened for tuberculosis (TB), and a rational approach to screening is required. We evaluated positive tuberculin skin tests (TSTs) and interferon-gamma release assays (IGRAs) on paediatric migrants in relation to the TB incidence in the corresponding foreign-born populations in Stockholm.

METHODS

This study examined the characteristics of migrants under the age of 18 who were referred to a paediatric TB clinic at Karolinska University Hospital from 2008 to 2014 by primary care centres in Stockholm County.

RESULTS

We saw 943 TST-positive children with a median age of 14 years at the TB clinic and performed IGRAs on 557. IGRA positivity ranged from 64% in migrants from Somalia to 20% in those from the former Soviet Union and eastern Europe, with an estimated population level prevalence of 18.8% and 4.2%, respectively. These were significantly correlated to TB incidence in foreign-born Stockholm children. We diagnosed active TB in 20 screened migrants, and advanced, symptomatic TB was diagnosed in 10 recently arrived migrants without screening.

CONCLUSION

IGRAs showed higher specificity than TST in identifying tuberculosis. TB screening should focus on migrants from high-incidence countries, but this may be inadequate to detect advanced TB cases.

Influenza epidemiology among hospitalized children in Stockholm, Sweden 1998-2014

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.

The aetiology of paediatric bloodstream infections changes after pneumococcal vaccination and group B streptococcus prophylaxis

AIM

This study explored the incidence and aetiology of bloodstream infections after patients received the pneumococcal conjugate vaccination and a risk-based intrapartum antibiotic prophylaxis against early onset sepsis caused by group B streptococcus. We also monitored clinically relevant antimicrobial resistance.

METHOD

We studied 3986 positive blood cultures from children up to 17 years of age at a paediatric hospital in Stockholm, Sweden, using data from medical records before and after the initiatives, to reduce early onset sepsis, were introduced in 2007 and 2008.

RESULTS

Bloodstream infections caused by Streptococcus pneumoniae declined by 42% overall (5.6 to 3.2/100 000) and by 62% in previously healthy children under 36 months of age (24.2 to 9.2/100 000). Early onset sepsis caused by group B streptococcus declined by 60% (0.5 to 0.2/1000 live born children). Bacterial meningitis caused by these bacteria decreased by 70%. Staphylococcus aureus and various Gram-negative bacteria became the dominant pathogens, in both previously healthy children and those with underlying disease. Overall, antimicrobial resistance remained low between the two 5-year study periods.

CONCLUSION

Pneumococcal conjugate vaccination and risk-based intrapartum antibiotic prophylaxis against group B streptococcus effectively decreased the incidence of bloodstream infections. Empirical antibiotic therapy should target Staphylococcus aureus in both community and hospital-acquired invasive bacterial infections.

Long term effectiveness of adjuvanted influenza A(H1N1)pdm09 vaccine in children

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.

Sinusitis and pneumonia hospitalization after introduction of pneumococcal conjugate vaccine

BACKGROUND AND OBJECTIVE

Streptococcus pneumoniae is a major cause of pneumonia and sinusitis. Pneumonia kills >1 million children annually, and sinusitis is a potentially serious pediatric disease that increases the risk of orbital and intracranial complications. Although pneumococcal conjugate vaccine (PCV) is effective against invasive pneumococcal disease, its effectiveness against pneumonia is less consistent, and its effect on sinusitis is not known. We compared hospitalization rates due to sinusitis, pneumonia, and empyema before and after sequential introduction of PCV7 and PCV13.

METHOD

All children 0 to <18 years old hospitalized for sinusitis, pneumonia, or empyema in Stockholm County, Sweden, from 2003 to 2012 were included in a population-based study of hospital registry data on hospitalizations due to sinusitis, pneumonia, or empyema. Trend analysis, incidence rates, and rate ratios (RRs) were calculated comparing July 2003 to June 2007 with July 2008 to June 2012, excluding the year of PCV7 introduction.

RESULTS

Hospitalizations for sinusitis decreased significantly in children aged 0 to <2 years, from 70 to 24 cases per 100 000 population (RR = 0.34, P < .001). Hospitalizations for pneumonia decreased significantly in children aged 0 to <2 years, from 450 to 366 per 100 000 population (RR = 0.81, P < .001) and in those aged 2 to <5 years from 250 to 212 per 100 000 population (RR = 0.85, P = .002). Hospitalization for empyema increased nonsignificantly. Trend analyses showed increasing hospitalization for pneumonia in children 0 to <2 years before intervention and confirmed a decrease in hospitalizations for sinusitis and pneumonia in children aged 0 to <5 years after intervention.

CONCLUSIONS

PCV7 and PCV13 vaccination led to a 66% lower risk of hospitalization for sinusitis and 19% lower risk of hospitalization for pneumonia in children aged 0 to <2 years, in a comparison of 4 years before and 4 years after vaccine introduction.

Age and risk factors influence the microbial aetiology of bloodstream infection in children

AIM

To study the aetiology of bloodstream infections (BSI) in children 0-17 years, the influence of age and underlying co-morbidity on BSI rate, distribution of pathogens and outcome; and to provide data on antimicrobial susceptibility patterns.

METHODS

A retrospective population-based study. Data on blood cultures were collected at yearly intervals during 1998-2008. Information about risk factors, focal infection and outcome was retrieved from the patient charts.

RESULTS

We identified 1097 BSI. The incidence of BSI was 0.4/1000. The age-specific incidence was 2.3/1000 in neonates (0-28 days old) and 0.2/1000 in the age group 6-17 years. Staphylococcus aureus was the most common pathogen. The number of species causing BSI in previously healthy children was lower compared with children with co-morbidity. Most children requiring intensive care had a serious underlying illness. Antimicrobial resistance was rare and did not influence outcome. The case-fatality rate was 14.4% in neonates, 5.4% in children with co-morbidity and 1.7% in previously healthy children.

CONCLUSION

Mortality from BSI is low, and a limited spectrum of pathogens is isolated from previously healthy children compared with children with co-morbidity. When choosing empirical therapy for suspected BSI, age and presence of risk factors should be taken into account.

Nerve dysfunction following surgical treatment of cervical non-tuberculous mycobacterial lymphadenitis in children

AIM

To present our experience of nerve dysfunction following surgical treatment among 126 children with microbiologically verified non-tuberculous mycobacterial (NTM) lymphadenitis.

METHODS

We retrieved data from medical records, and a questionnaire with an invitation to a clinical follow-up was returned by 88 families.

RESULTS

The time from onset of symptoms to diagnosis was more than 3 months in 24% of subjects. Mycobacterium avium complex was isolated from 105, Mycobacterium malmoense from 12 and Mycobacterium scrofulaceum from one cervical lymph node. A total of 89% of the children underwent surgery and were examined in particular with regard to cranial motor nerve functions. Major persisting nerve dysfunction occurred in 3/51 (6%) children who underwent radical surgery, and minor dysfunction in seven (14%). In nine children, the marginal mandibular branch of the facial nerve was affected, and the accessory nerve was affected in one child. There were no neurological signs in 25 children treated with incision and drainage alone or in 12 followed with observation alone. Healing took >6 months in 2/76 (3%) surgically treated and 3/12 (25%) non-surgically treated children.

CONCLUSION

Considering the risk of nerve dysfunction following extirpation, incision with drainage and observation alone should both be included among the management options for cervical NTM lymphadenitis in children.

Complexity in estimating recent tuberculosis transmission among predominantly immigrant school children in Stockholm, Sweden 2006

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.

Primary tuberculosis infection in 35 children at a Swedish day care center

BACKGROUND AND METHOD

The decline of tuberculosis (TB) in the Swedish population since the middle of the 20th century resulted in decreased awareness of the disease. Increased migration from TB-endemic countries has resulted in new cases and risk of transmission. A day care provider was diagnosed with cavitary TB after being symptomatic for 5 months. We describe the contact tracing at the day care center, the clinical and radiographic findings, and treatment of the infected children.

RESULTS

We stratified the children by contact with the source case and examined the most exposed first. Thirty-two of 53 attending and 3 of 84 visiting preschool children were infected. All of them had spent at least 3 days at the center. Symptoms were usually mild and nonspecific. Seventeen children had pulmonary radiographic changes compatible with primary TB, and one had miliary TB. The radiographic resolution was slow, with normalization in 50% after 12 months. Eighteen months after termination of treatment, there have been no relapses. The children with latent infection were treated with rifampin for 4 months and none has developed TB.

CONCLUSIONS

The manifestations of primary TB in children today are similar to those described 50-70 years ago. The tuberculin skin test is an effective tool for contact tracing in an unvaccinated, previously nonexposed childhood population. Rapid detection of contagious patients and thorough contact investigation remain our most important means to reduce transmission.

Extensive transmission of an isoniazid-resistant strain of Mycobacterium tuberculosis in Sweden

SETTING

City of Stockholm, Sweden.

BACKGROUND

The incidence of tuberculosis (TB) in Sweden increased by 40% between 2003 and 2005. The spread of a unique TB strain resistant to isoniazid (INH) contributed to this increase.

OBJECTIVE

To describe outbreaks of TB caused by this single strain, elucidate possible causes for its extensive spread and identify shortcomings of the TB control programme in Sweden.

RESULTS

We identified a cluster consisting of 102 culture-confirmed TB cases with identical DNA fingerprints and 26 epidemiologically related cases, not confirmed by culture, all diagnosed between 1996 and 2005. Five partly separate outbreaks of this strain were discovered. Epidemiological links were established for 56% of the culture-confirmed cases and for all cases not confirmed by culture. Three patients died while receiving treatment, four became failures and eight defaulted or were lost to follow-up. Only eight patients received directly observed treatment (DOT) up to a period of 3 months, although 40% had poor adherence.

CONCLUSIONS

Shortcomings of the national TB programme were revealed. Improved contact tracing and case holding, including DOT, is crucial to reduce TB transmission in Sweden.

Outbreak of tuberculosis in a Stockholm nursery affects 35 children

A female assistant at a nursery in a wealthy suburb of Stockholm was diagnosed with smear positive advanced pulmonary tuberculosis in August 2005.

Palivizumab prophylaxis and hospitalization for respiratory syncytial virus disease in the Stockholm infant population, 1999 through 2002

BACKGROUND

There are few independent, population-based reports that estimate the risk of hospitalization of respiratory syncytial virus (RSV)-infected infants before and during the palivizumab era. We present figures from the greater Stockholm area during the three seasons after the introduction of palivizumab and relate them to data based on 1400 hospitalizations for RSV disease in the same population area during 1987 through 1998.

METHODS

The number of births, neonatal complications and palivizumab prescriptions was obtained. We retrieved information about all infant hospitalizations for confirmed RSV infections with risk factors and complications. Chronic lung disease (CLD) in preterm infants was defined as oxygen dependency beyond 36 weeks of postconceptional age.

RESULTS

Eight hundred eighteen infants (1.3% of the population) were hospitalized for confirmed RSV infection. The hospitalization rates were 3.7% (24 of 642) among preterm infants with gestational age <33 weeks without CLD and 7.2% (14 of 195) in those with CLD. Palivizumab had been given to 235 infants, usually those with CLD and in need of continuous oxygen or steroid treatment or the <6 month-old infants with extremely preterm birth (gestational age <26 weeks). The risk of hospitalization for RSV disease was low, but this was the case also before the introduction of palivizumab.

CONCLUSIONS

In countries with a low baseline risk of hospitalization for RSV infection, the benefit of palivizumab might not justify the cost of its widespread use. We advocate defining more rigorous prescription criteria.

Population-based rates of severe respiratory syncytial virus infection in children with and without risk factors, and outcome in a tertiary care setting

The aim of this study was to make a population-based estimate of the risk of hospitalization and complications during virologically confirmed respiratory syncytial virus (RSV) infection in relation to established risk factors, and an estimation of additional risk factors and outcome as seen in a tertiary care referral centre. During a period of 12 y, all children with virologically confirmed RSV infection were included. Recorded complications were: admission to the intensive care unit, mechanical ventilation, death and later hospitalization for wheezing. In total, 1503 cases were identified, 1354 of which originated from the population defined by the catchment area. There was a biannual seasonal variation with late small outbreaks alternating with early large ones. The hospitalization rates for infants without risk factors were 0.8 and 1.4% during the 2 epidemic types. They were 1.6-3.2% for infants born preterm (<33 gestational wk), 2.9-7.0% for children under 2 y old with chronic lung disease of prematurity and 2.8-6.4% for infants with congenital heart disease. The presence of siblings in the family more than doubled the risk of hospitalization. Later hospitalization for wheezing occurred in 8.4 and 4.9% of children without risk factors over and under the age of 2 mo, respectively (p < 0.001).

CONCLUSION

This study found lower population rates of hospitalization and complications than have previously been reported. The seasonal variation and the presence of siblings in the home influenced these rates by factors of 2.

Successful treatment of neuroborreliosis with ten day regimens

BACKGROUND

There have been few large reports of the treatment and outcome of neuroborreliosis in children.

METHODS

All 203 children with symptoms, cerebrospinal fluid and serologic findings compatible with neuroborreliosis and treated at one of the four pediatric hospitals in Stockholm from 1994 through 1996 were included. Children were treated with intravenous beta-lactam antibiotics or oral doxycycline for 10 days and followed until the resolution of symptoms.

RESULTS

At the end of treatment 58% and after 2 months 92% of the children had no symptoms. Cerebrospinal fluid findings had no statistically significant influence on the outcome. Facial paralysis persisted longer than other symptoms.

CONCLUSIONS

The prognosis of neuroborreliosis in children 2 months after treatment seems to be excellent with 10-day treatment regimens.

The fecal microflora of 1-3-month-old infants during treatment with eight oral antibiotics

We examined the fecal microflora of 1-3-month-old infants during treatment with phenoxymethylpenicillin, amoxycillin, pivampicillin, cefaclor, cefadroxil, loracarbef, erythromycin or cotrimoxazole. Escherichia coli increased during treatment with penicillins or cephalosporins, but was not affected by erythromycin or cotrimoxazole. Other enterobacteria were acquired or increased during treatment with all agents except cotrimoxazole. Enterococci persisted or increased during phenoxymethylpenicillin, cephalosporin or cotrimoxazole treatment, whereas erythromycin and the other penicillins suppressed them. Bacteroides, bifidobacteria and lactobacilli were suppressed to undetectable levels in most infants during treatment with all agents, except phenoxymethylpenicillin and loracarbef.

Non-tuberculous mycobacterial lymphadenitis in healthy children: another "lifestyle disease"?

An increasing incidence of non-tuberculous mycobacterial (NTM) lymphadenitis has been reported in previously healthy children in the western world since about 1985. In this study we investigated the sociodemographic and individual characteristics of these patients. Information about patients was collected prospectively from 1977 to 1996. For comparison, an ad hoc group of hospitalized children with bacterial cervical lymphadenitis was chosen. In addition to individual characteristics, information was collected on the country of birth of the patients and their parents, and the socioeconomic characteristics of the domicile area. We identified 81 children with NTM, 14 with tuberculous and 192 with septic lymphadenitis. Significantly more parents of children with NTM than in either of the other two groups were Swedish-born and lived in privileged socioeconomic areas.

CONCLUSION

The increase in NTM lymphadenitis in healthy children has taken place at the same time as the reported increase in atopic disease and asthma in childhood. Both groups of patients seem to come from favourable living conditions. It is speculated that NTM lymphadenitis, like asthma and certain other diseases triggered by the immune system, might be a "lifestyle disease".