Risk factors associated with severe influenza infections in childhood: implication for vaccine strategy

Prescription of anti-influenza drugs in Japan, 2014-2020: A retrospective study using open data from the national claims database

BACKGROUND

Both physicians and patients are proactive towards managing seasonal influenza in Japan and six drugs are approved. Although many countries have national influenza surveillance systems, data on nationwide prescription practices of anti-influenza drugs are lacking. Therefore, we aimed to clarify the status of anti-influenza drug use in Japan by analyzing real-world data.

METHODS

This retrospective study analyzed open data from the National Database of Health Insurance Claims and Specific Health Checkups, which covers most claims data from national health insurance. We estimated the annual number of patients prescribed anti-influenza drugs, which drugs they were prescribed, the patients' age and sex distribution, drug costs, and regional disparities for the period 2014-2020.

RESULTS

For 2014-2019, an estimated 6.7-13.4 million patients per year were prescribed anti-influenza drugs, with an annual cost of 22.3-48.0 billion JPY (Japanese Yen). In addition, 21.1-32.0 million rapid antigen tests were performed at a cost of 30.1-47.1 billion JPY. In 2017, laninamivir was the most frequently prescribed anti-influenza drug (48%), followed by oseltamivir (36%), while in 2018, the newly introduced baloxavir accounted for 40.8% of prescriptions. After the emergence of COVID-19, the estimated number of patients prescribed anti-influenza drugs in 2020 dropped to just 14,000. In 2018, 37.6% of prescriptions were for patients aged < 20 years compared with 12.2% for those aged ≥ 65 years. Prescriptions for inpatients accounted for 1.1%, and the proportion of prescriptions for inpatients increased with age, with men were more likely than women to be prescribed anti-influenza drugs while hospitalized.

CONCLUSIONS

Based on our clarification of how influenza is clinically managed in Japan, future work should evaluate the clinical and economic aspects of proactively prescribing anti-influenza drugs.

Profiling of innate and adaptive immune cells during influenza virus infection reveals sex bias in invariant natural killer T (iNKT) cells

BACKGROUND

Influenza A virus (IAV) infection leads to significant morbidity and mortality. Biological sex influences the immune responses to IAV infection, resulting in higher mortality in women of reproductive age. Previous studies revealed increased activation of T and B cells in female mice after IAV infection, but extensive analysis of sex differences in both innate and adaptive immune cells over time is lacking. Invariant natural killer T (iNKT) cells are fast-reacting forces and modulators of immune responses that are important to IAV immunity, but it is not known if the presence and function of iNKT cells differ between females and males. The aim of this study was to determine immunological mechanisms that contribute to the increased disease severity in female mice during IAV infection.

METHODS

Female and male mice were infected with mouse-adapted IAV and monitored for weight loss and survival. Immune cell populations and cytokine expression in bronchoalveolar lavage fluid, lung, and mediastinal lymph node were determined at three time points after infection using flow cytometry and ELISA.

RESULTS

The results reveal increased severity and mortality in adult female mice compared to age-matched males. Female mice show larger increases in innate and adaptive immune cell populations and cytokine production in lung compared to mock on Day 6 postinfection. On Day 9 postinfection, female mice express higher numbers of iNKT cells in lung and liver compared to males.

CONCLUSIONS

This comprehensive analysis of immune cells and cytokines over time following IAV infection reveals increased leukocyte expansion and stronger proinflammatory cytokine responses in female mice during disease initiation. Furthermore, this is the first study to report a sex bias in iNKT cell populations after IAV infection. The data suggests that the process of recovery from IAV-induced airway inflammation is associated with increased expansion of several different iNKT cell subpopulations in female mice.

Clinical characteristics and mortality risk factors in patients aged less than 18 years with COVID-19 in Mexico and Mexico City

Introduction

Methods

Results

Conclusion

[Clinical Characteristics And Mortality Risk Factors In Patients Aged Less Than 18 Years With Covid-19 In Mexico And Mexico City]

INTRODUCTION

In the paediatric population, coronavirus disease (COVID-19) is usually asymptomatic or mild, but there are also severe and fatal cases.

METHODS

We analysed data on COVID-19 cases from the national and state-level databases of the Federal Ministry of Health of Mexico and the Department of Health of Mexico City to determine the clinical characteristics and risk factors for mortality in children. We used Cox proportional hazards regression analysis to calculate the risk of death.

RESULTS

The national and Mexico City databases had recorded a total of 18 465 (2.8%) and 5733 (4.2%) confirmed cases of COVID-19, respectively, in individuals aged less than 18 years as of September 2020. The median age at diagnosis was 12 years (range, 0-17). The differences between cases in the national vs Mexico City databases were: 12.5% vs 8.2% of patients were hospitalized; 6% vs 3.5% had pneumonia; 2.4% vs 1.9% were admitted to the intensive care unit (ICU), and 1.3% vs 0.7% died. The independent risk factors significantly associated with a higher probability of death were pneumonia, hypertension, obesity, immunosuppression and intubation.

CONCLUSION

In Mexico, 2.8% of all confirmed cases of COVID-19 occurred in individuals under 18 years, with a median age of 12 years and a mortality of 1.3%. The identified predictors of mortality were pneumonia, admission to the ICU, obesity, hypertension, immunosuppression, diabetes, chronic lung disease and renal disease.

Clinical Practice Guidelines by the Infectious Diseases Society of America: 2018 Update on Diagnosis, Treatment, Chemoprophylaxis, and Institutional Outbreak Management of Seasonal Influenzaa

These clinical practice guidelines are an update of the guidelines published by the Infectious Diseases Society of America (IDSA) in 2009, prior to the 2009 H1N1 influenza pandemic. This document addresses new information regarding diagnostic testing, treatment and chemoprophylaxis with antiviral medications, and issues related to institutional outbreak management for seasonal influenza. It is intended for use by primary care clinicians, obstetricians, emergency medicine providers, hospitalists, laboratorians, and infectious disease specialists, as well as other clinicians managing patients with suspected or laboratory-confirmed influenza. The guidelines consider the care of children and adults, including special populations such as pregnant and postpartum women and immunocompromised patients.

Is there a difference in the immune response, efficacy, effectiveness and safety of seasonal influenza vaccine in males and females? - A systematic review

INTRODUCTION

Seasonal influenza is an important cause of morbidity and mortality, despite being vaccine-preventable. Sex factors (genes and hormones) seem to impact individuals' susceptibility to infectious diseases and their response to vaccination. However, most vaccine studies do not explicitly assess sex differences in vaccine response, but rather adjust for sex.

METHODS

We conducted a systematic review to analyze immunogenicity, efficacy, effectiveness and/or safety of seasonal influenza vaccine data stratified by sex. We searched PubMed, EMBASE, CINAHL, Web of Science and clinicaltrials.gov for observational studies and phase III/IV trials from January 1990 to June 2018, published in English or French. Two reviewers independently screened all references, then proceeded to data extraction and quality assessment using the Cochrane tools (RoB and ROBINS-I) on included studies.

RESULTS

Of the 5,745 citations retrieved, 46 studies were included in the SR. Overall, 18 studies assessed immunogenicity, 1 estimated efficacy, 6 measured effectiveness and 25 evaluated safety of seasonal influenza vaccine in females and males (four studies reported on two sex-stratified outcomes concomitantly).

CONCLUSION

No clear conclusion could be drawn regarding the effect of sex on the immunogenicity and effectiveness of seasonal influenza vaccine, but higher rates of adverse events following immunization (AEFIs) were reported in females. The heterogeneity of data and studies' low quality prevented us from conducting a meta-analysis. There is a need to emphasize on the appropriate use of the terms sex and gender in biomedical research. Evidence of higher quality is needed to better understand sex differences in response to influenza vaccine.

Epidemiological and clinical characteristics of children hospitalized due to influenza A and B in the south of Europe, 2010-2016

Influenza produces annual epidemics that affect 5–15% of the world population. Complications and hospitalizations are more frequent in childhood. This study describes and analyses the epidemiological and clinical characteristics of children hospitalized due to confirmed influenza in influenza surveillance sentinel hospitals in Catalonia. Retrospective descriptive study conducted in six influenza seasons (2010–2011 to 2015–2016) in persons aged 0–17 years diagnosed with laboratory-confirmed influenza requiring hospitalization. 291 cases were notified to the health authorities: 79.4% were due to the influenza A virus and 20.6% to the B virus. The most common subtype was H1N1 with 57.6% of cases: 52.6% were male, 56.7% were aged <2 years, and 24.4% were aged <1 year. 62.2% of cases had pneumonia, 26.8% acute respiratory distress syndrome and 11.7% bacterial pneumonia. 5.8% of cases were vaccinated and 21.3% required intensive care unit admission, of whom 54.8% were aged <2 years. There were 3 deaths, all with influenza A infection. Influenza A cases were younger than influenza B cases (OR 3.22; 95% CI: 1.73–6.00). Conclusion: Children aged <2 years are especially vulnerable to the A H1N1 virus, including those without pre-existing chronic disease. These results are relevant for the planning of vaccination programs to improve maternal and child health.

The intersection of sex and gender in the treatment of influenza

Males/men and females/women differ in the outcome of influenza A virus (IAV) infections, vaccination, and antiviral treatments. Both sex (i.e. biological factors) and gender (i.e. sociocultural factors) can impact exposure and severity of IAV infections as well as responses and outcomes of treatments for IAV. Greater consideration of the combined effects of sex and gender in epidemiological, clinical, and animal studies of influenza pathogenesis is needed.

Clinical Practice Guidelines by the Infectious Diseases Society of America: 2018 Update on Diagnosis, Treatment, Chemoprophylaxis, and Institutional Outbreak Management of Seasonal Influenzaa

These clinical practice guidelines are an update of the guidelines published by the Infectious Diseases Society of America (IDSA) in 2009, prior to the 2009 H1N1 influenza pandemic. This document addresses new information regarding diagnostic testing, treatment and chemoprophylaxis with antiviral medications, and issues related to institutional outbreak management for seasonal influenza. It is intended for use by primary care clinicians, obstetricians, emergency medicine providers, hospitalists, laboratorians, and infectious disease specialists, as well as other clinicians managing patients with suspected or laboratory-confirmed influenza. The guidelines consider the care of children and adults, including special populations such as pregnant and postpartum women and immunocompromised patients.

Sex and sex steroids impact influenza pathogenesis across the life course

Males and females differ in the outcome of influenza A virus (IAV) infections, which depends significantly on age. During a typical seasonal influenza epidemic, young children (< 10 years of age) and aged adults (65+ years of age) are at greatest risk for severe disease, and among these age groups, males tend to suffer a worse outcome from IAV infection than females. Following infection with either pandemic or outbreak strains of IAVs, females of reproductive ages (i.e., 15-49 years of age) experience a worse outcome than their male counterparts. Among females of reproductive ages, pregnancy is one factor linked to an increased risk of severe outcome of influenza, although it is not the sole factor explaining the female-preponderance of severe disease. Small animal models of influenza virus infection illustrate that inflammatory immune responses and repair of damaged tissue following IAV infection also differ between the sexes and impact the outcome of infection. There also is growing evidence that sex steroid hormones, including estrogens, progesterone, and testosterone, directly impact immune responses during IAV infection to alter outcomes. Greater consideration of the combined effects of sex and age as biological variables in epidemiological, clinical, and animal studies of influenza pathogenesis is needed.

Severe Obesity in Children May Not Pose Independent Risk for Influenza Complications

PURPOSE

Subsets of children are targeted for influenza vaccination due to known conditions that increase the risk of influenza complications. The purpose of this study was to determine if severe obesity in children suggests targeted vaccination.

DESIGN AND METHODS

A retrospective chart review of a large Midwestern pediatric hospital identified 188 cases of influenza complications (defined as requiring hospitalization or death) aged 2 to <20 years old from August 1, 2010 through June 30, 2013. Severe obesity was defined as body mass index (BMI) ≥99% for age and gender, with patients grouped by severe obesity status (yes vs. no). Cases were reviewed for previously identified risk conditions for influenza complications (e.g., asthma, pneumonia, diabetes), and were classified as having or not having a known high risk condition.

RESULTS

Of 188 cases, 174 (93%) had a high-risk condition, while only 14 (7%) had no known condition. All 14 (100%) with no known high-risk condition had a BMI <99%. All 15 (100%) with BMI ≥99% had a known high-risk condition. The association between severe obesity status and influenza complications was not statistically significant (p = 0.61).

CONCLUSIONS

This suggests that severe obesity in children is not an independent high-risk condition for influenza complications defined as requiring hospitalization or resulting in death, once other known influenza risk factors are considered.

IMPLICATIONS

Based on this data, clinicians should not target children for influenza vaccination based on weight status. We cannot comment about whether severe obesity represents increased risk for less severe cases of influenza.

Influenza-Associated Pediatric Deaths in the United States, 2010-2016

BACKGROUND

Influenza-associated pediatric deaths became a notifiable condition in the United States in 2004.

METHODS

We analyzed deaths in children aged <18 years with laboratory-confirmed influenza virus infection reported to the Centers for Disease Control and Prevention during the 2010-2011 to 2015-2016 influenza seasons. Data were collected with a standard case report form that included demographics, medical conditions, and clinical diagnoses.

RESULTS

Overall, 675 deaths were reported. The median age was 6 years (interquartile range: 2-12). The average annual incidence was 0.15 per 100 000 children (95% confidence interval: 0.14-0.16) and was highest among children aged <6 months (incidence: 0.66; 95% confidence interval: 0.53-0.82), followed by children aged 6-23 months (incidence: 0.33; 95% confidence interval: 0.27-0.39). Only 31% (n = 149 of 477) of children aged ≥6 months had received any influenza vaccination. Overall, 65% (n = 410 of 628) of children died within 7 days after symptom onset. Half of the children (n = 327 of 654) had no preexisting medical conditions. Compared with children with preexisting medical conditions, children with none were younger (median: 5 vs 8 years old), less vaccinated (27% vs 36%), more likely to die before hospital admission (77% vs 48%), and had a shorter illness duration (4 vs 7 days; P < .05 for all).

CONCLUSIONS

Each year, influenza-associated pediatric deaths are reported. Young children have the highest death rates, especially infants aged <6 months. Increasing vaccination among children, pregnant women, and caregivers of infants may reduce influenza-associated pediatric deaths.

Vaccines for preventing influenza in healthy children

BACKGROUND

The consequences of influenza in children and adults are mainly absenteeism from school and work. However, the risk of complications is greatest in children and people over 65 years of age. This is an update of a review published in 2011. Future updates of this review will be made only when new trials or vaccines become available. Observational data included in previous versions of the review have been retained for historical reasons but have not been updated because of their lack of influence on the review conclusions.

OBJECTIVES

To assess the effects (efficacy, effectiveness, and harm) of vaccines against influenza in healthy children.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (the Cochrane Library 2016, Issue 12), which includes the Cochrane Acute Respiratory Infections Group Specialised Register, MEDLINE (1966 to 31 December 2016), Embase (1974 to 31 December 2016), WHO International Clinical Trials Registry Platform (ICTRP; 1 July 2017), and ClinicalTrials.gov (1 July 2017).

SELECTION CRITERIA

Randomised controlled trials comparing influenza vaccines with placebo or no intervention in naturally occurring influenza in healthy children under 16 years. Previous versions of this review included 19 cohort and 11 case-control studies. We are no longer updating the searches for these study designs but have retained the observational studies for historical purposes.

DATA COLLECTION AND ANALYSIS

Review authors independently assessed risk of bias and extracted data. We used GRADE to rate the certainty of evidence for the key outcomes of influenza, influenza-like illness (ILI), complications (hospitalisation, ear infection), and adverse events. Due to variation in control group risks for influenza and ILI, absolute effects are reported as the median control group risk, and numbers needed to vaccinate (NNVs) are reported accordingly. For other outcomes aggregate control group risks are used.

MAIN RESULTS

We included 41 clinical trials (> 200,000 children). Most of the studies were conducted in children over the age of two and compared live attenuated or inactivated vaccines with placebo or no vaccine. Studies were conducted over single influenza seasons in the USA, Western Europe, Russia, and Bangladesh between 1984 and 2013. Restricting analyses to studies at low risk of bias showed that influenza and otitis media were the only outcomes where the impact of bias was negligible. Variability in study design and reporting impeded meta-analysis of harms outcomes.Live attenuated vaccinesCompared with placebo or do nothing, live attenuated influenza vaccines probably reduce the risk of influenza infection in children aged 3 to 16 years from 18% to 4% (risk ratio (RR) 0.22, 95% confidence interval (CI) 0.11 to 0.41; 7718 children; moderate-certainty evidence), and they may reduce ILI by a smaller degree, from 17% to 12% (RR 0.69, 95% CI 0.60 to 0.80; 124,606 children; low-certainty evidence). Seven children would need to be vaccinated to prevent one case of influenza, and 20 children would need to be vaccinated to prevent one child experiencing an ILI. Acute otitis media is probably similar following vaccine or placebo during seasonal influenza, but this result comes from a single study with particularly high rates of acute otitis media (RR 0.98, 95% CI 0.95 to 1.01; moderate-certainty evidence). There was insufficient information available to determine the effect of vaccines on school absenteeism due to very low-certainty evidence from one study. Vaccinating children may lead to fewer parents taking time off work, although the CI includes no effect (RR 0.69, 95% CI 0.46 to 1.03; low-certainty evidence). Data on the most serious consequences of influenza complications leading to hospitalisation were not available. Data from four studies measuring fever following vaccination varied considerably, from 0.16% to 15% in children who had live vaccines, while in the placebo groups the proportions ranged from 0.71% to 22% (very low-certainty evidence). Data on nausea were not reported.Inactivated vaccinesCompared with placebo or no vaccination, inactivated vaccines reduce the risk of influenza in children aged 2 to 16 years from 30% to 11% (RR 0.36, 95% CI 0.28 to 0.48; 1628 children; high-certainty evidence), and they probably reduce ILI from 28% to 20% (RR 0.72, 95% CI 0.65 to 0.79; 19,044 children; moderate-certainty evidence). Five children would need to be vaccinated to prevent one case of influenza, and 12 children would need to be vaccinated to avoid one case of ILI. The risk of otitis media is probably similar between vaccinated children and unvaccinated children (31% versus 27%), although the CI does not exclude a meaningful increase in otitis media following vaccination (RR 1.15, 95% CI 0.95 to 1.40; 884 participants; moderate-certainty evidence). There was insufficient information available to determine the effect of vaccines on school absenteeism due to very low-certainty evidence from one study. We identified no data on parental working time lost, hospitalisation, fever, or nausea.We found limited evidence on secondary cases, requirement for treatment of lower respiratory tract disease, and drug prescriptions. One brand of monovalent pandemic vaccine was associated with a sudden loss of muscle tone triggered by the experience of an intense emotion (cataplexy) and a sleep disorder (narcolepsy) in children. Evidence of serious harms (such as febrile fits) was sparse.

AUTHORS' CONCLUSIONS

In children aged between 3 and 16 years, live influenza vaccines probably reduce influenza (moderate-certainty evidence) and may reduce ILI (low-certainty evidence) over a single influenza season. In this population inactivated vaccines also reduce influenza (high-certainty evidence) and may reduce ILI (low-certainty evidence). For both vaccine types, the absolute reduction in influenza and ILI varied considerably across the study populations, making it difficult to predict how these findings translate to different settings. We found very few randomised controlled trials in children under two years of age. Adverse event data were not well described in the available studies. Standardised approaches to the definition, ascertainment, and reporting of adverse events are needed. Identification of all global cases of potential harms is beyond the scope of this review.

Influenza and respiratory syncytial virus in infants study (IRIS) of hospitalized and non-ill infants aged <1 year in four countries: study design and methods

Background

This multi-country prospective study of infants aged <1 year aims to assess the frequency of influenza virus and respiratory syncytial virus (RSV) infections associated with hospitalizations, to describe clinical features and antibody response to infection, and to examine predictors of very severe disease requiring intensive care.

Methods/Design

We are enrolling a hospital-based cohort and a sample of non-ill infants in four countries (Albania, Jordan, Nicaragua, and the Philippines) using a common protocol. We are currently starting year 2 of a 2- to 3-year study and will enroll approximately 3,000 infants hospitalized for any acute illness (respiratory or non-respiratory) during periods of local influenza and/or RSV circulation. After informed consent and within 24 h of admission, we collect blood and respiratory specimens and conduct an interview to assess socio-demographic characteristics, medical history, and symptoms of acute illness (onset ≤10 days). Vital signs, interventions, and medications are documented daily through medical record abstraction. A follow-up health assessment and collection of convalescent blood occurs 3-5 weeks after enrollment. Influenza and RSV infection is confirmed by singleplex real time reverse transcriptase polymerase chain reaction (rRT-PCR) assays. Serologic conversion will be assessed comparing acute and convalescent sera using hemagglutination inhibition assay for influenza antibodies and enzyme-linked immunosorbent assay (ELISA) for RSV. Concurrent with hospital-based enrollment, respiratory specimens are also being collected (and tested by rRT-PCR) from approximately 1,400 non-ill infants aged <1 year during routine medical or preventive care.

Discussion

The Influenza and RSV in Infants Study (IRIS) promises to expand our knowledge of the frequency, clinical features, and antibody profiles of serious influenza and RSV disease among infants aged <1 year, quantify the proportion of infections that may be missed by traditional surveillance, and inform decisions about the potential value of existing and new vaccines and other prevention and treatment strategies.

Risk factors associated with hospitalisation for influenza-associated severe acute respiratory illness in South Africa: A case-population study

BACKGROUND

Influenza is a common cause of severe respiratory illness, but risk factors for hospitalisation in low income settings with a high HIV prevalence are not well described. We aimed to assess risk factors associated with influenza-associated severe acute respiratory illness (SARI) hospitalisation in South Africa.

METHODS

We conducted a case-population study using data on risk conditions in patients hospitalised with SARI and the national prevalence of these conditions. Data on hospitalised cases were from the national SARI surveillance program while data on the referent population were from the latest national census or health and demographic surveillance surveys.

FINDINGS

From 2009 to 2012, we identified 3646 (7.9%) of 46,031 enrolled cases of SARI that were associated with influenza infection. Risk factors associated with hospitalisation included previous history of smoking [case-population ratio (CPR) 3.82, 95% confidence interval (CI) 3.5-4.16], HIV infection (CPR 3.61, 95% CI 3.5-3.71), asthma (CPR 2.45, 95% CI 2.19-2.73), previous history of hospital admission in the past 12months (CPR 2.07, 95% CI 1.92-2.23), and tuberculosis (CPR 1.85, 95% CI 1.68-2.02). When stratified by age, there is increased risk of hospitalisation in those ⩽5yearsof age (CPR 3.07, 95% CI 2.93-3.21) and among those 35yearsof age and above (CPR 1.23, 95% CI 1.28-1.18). Male sex (CPR 0.85, 95% CI 0.82-0.88) and completion of pneumococcal conjugate vaccination schedule in children <5yearsof age (CPR 0.74, 95% CI 0.71-0.77) were associated with decreased risk of hospitalisation.

CONCLUSION

These results identify groups at high-risk for severe influenza who should be considered potential targets for influenza vaccination in South Africa and similar settings.

Contribution of influenza viruses to medically attended acute respiratory illnesses in children in high-income countries: a meta-analysis

AIM

The burden of disease in children attributable to influenza viruses is difficult to quantify given the similarity of symptoms caused by infection due to influenza and other viruses. This uncertainty impacts clinical decision-making and estimates of burden. We aimed to systematically review the literature to determine the proportion of healthy children presenting for health care with an acute respiratory illness (ARI) who have laboratory-confirmed seasonal influenza (PROSPERO ID#CRD42014013896).

METHOD

We searched Ovid MEDLINE, EMBASE, Scopus, and references of included articles. We included studies that used polymerase chain reaction methods to test for influenza in healthy children aged ≤5 years who presented for health care in high-income countries with an influenza-like or ARI. A standardized form was used to collect data on positivity and other relevant study elements.

RESULTS

Seventeen studies covering 12 different influenza seasons were included. The proportion of influenza positivity ranged from 11% to 56%. Subgroup analyses were performed by influenza season, continent, healthcare setting, age group, and vaccination status. Higher influenza positivity was reported among children aged 3-5 years compared with children aged ≤2 years, and for unvaccinated children.

CONCLUSION

The minority of healthy patients aged ≤5 years with medically attended influenza-like or acute respiratory symptoms have laboratory-confirmed influenza virus infection, although this varied by influenza season. Prevention efforts should be targeted accordingly.

STATEMENT

Most influenza-like illnesses are not laboratory-confirmed and have similar clinical presentations. Consequently, the true contribution of influenza to acute respiratory infections in children remains uncertain. Our systematic review estimates that this proportion ranges from 11% to 56%. This finding can help both clinicians and public health professionals target prevention.

Improving influenza vaccination in chronically ill children using a tertiary-care based vaccination clinic: Is there a role for the live-attenuated influenza vaccine (LAIV)?

BACKGROUND

Children with underlying medical conditions should receive influenza vaccine (IV) yearly; yet this remains sub-optimal. We aimed to describe our experience with a tertiary-care hospital-based influenza vaccination clinic for this at-risk population.

METHODS

From October to December 2012, 2013, and 2014, we ran an influenza vaccination clinic at the Montreal Children's Hospital, where children with high-risk conditions come for their follow-up. Both injectable IV (IIV) and live-attenuated IV (LAIV) were offered free of charge to patients and their household contacts. Upon vaccination, parents were asked to fill a pre-piloted questionnaire.

RESULTS

We vaccinated a total of 2640 high-risk children and 1912 household members during the three influenza vaccination seasons. In 2012 and 2013, 631 and 630 patients with chronic illnesses were vaccinated, compared to 1379 in 2014. Caregivers preferred LAIV primarily because no needle was involved (49.0%) and because it was perceived as less painful (46.9%). LAIV was administered to 69% (2012), 55% (2013) and 47% (2014) of high-risk children. The main reason for not receiving LAIV was because it was contra-indicated. A small fraction of children previously vaccinated with LAIV who did not present any contraindication to LAIV opted for IIV: 12/101 (11.8%) in 2013 and 16/272 (5.9%) in 2014. In 2014, this was mainly due to a previous negative experience with LAIV (11/16).

CONCLUSION

Having an influenza vaccination clinic on site at a tertiary care hospital, where children come for their scheduled visits, facilitates yearly influenza vaccination in children with chronic illnesses. LAIV is preferred by caregivers and patients, when not contraindicated.

Continued high incidence of children with severe influenza A(H1N1)pdm09 admitted to paediatric intensive care units in Germany during the first three post-pandemic influenza seasons, 2010/11-2012/13

BACKGROUND

Previous influenza surveillance at paediatric intensive care units (PICUs) in Germany indicated increased incidence of PICU admissions for the pandemic influenza subtype A(H1N1)pdm09. We investigated incidence and clinical characteristics of influenza in children admitted to PICUs during the first three post-pandemic influenza seasons, using active screening.

METHODS

We conducted a prospective surveillance study in 24 PICUs in Bavaria (Germany) from October 2010 to September 2013. Influenza cases among children between 1 month and 16 years of age admitted to these PICUs with acute respiratory infection were confirmed by PCR analysis of respiratory secretions.

RESULTS

A total of 24/7/20 influenza-associated PICU admissions were recorded in the post-pandemic seasons 1/2/3; incidence estimates per 100,000 children were 1.72/0.76/1.80, respectively. Of all 51 patients, 80% had influenza A, including 65% with A(H1N1)pdm09. Influenza A(H1N1)pdm09 was almost absent in season 2 (incidence 0.11), but dominated PICU admissions in seasons 1 (incidence 1.35) and 3 (incidence 1.17). Clinical data was available for 47 influenza patients; median age was 4.8 years (IQR 1.6-11.0). The most frequent diagnoses were influenza-associated pneumonia (62%), bronchitis/bronchiolitis (32%), secondary bacterial pneumonia (26 %), and ARDS (21%). Thirty-six patients (77 %) had underlying medical conditions. Median duration of PICU stay was 3 days (IQR 1-11). Forty-seven per cent of patients received mechanical ventilation, and one patient (2%) extracorporeal membrane oxygenation; 19% were treated with oseltamivir. Five children (11%) had pulmonary sequelae. Five children (11%) died; all had underlying chronic conditions and were infected with A(H1N1)pdm09. In season 3, patients with A(H1N1)pdm09 were younger than in season 1 (p = 0.020), were diagnosed more often with bronchitis/bronchiolitis (p = 0.004), and were admitted to a PICU later after the onset of influenza symptoms (p = 0.041).

CONCLUSIONS

Active screening showed a continued high incidence of A(H1N1)pdm09-associated PICU admissions in the post-pandemic seasons 1 and 3, and indicated possible underestimation of incidence in previous German studies. The age shift of severe A(H1N1)pdm09 towards younger children may be explained by increasing immunity in the older paediatric population. The high proportion of patients with underlying chronic conditions indicates the importance of consistent implementation of the current influenza vaccination recommendations for risk groups in Germany.

Influenza vaccination during pregnancy and its usefulness to mothers and their young infants

The current approach to protecting pregnant women from influenza infection and serious influenza-related complications is vaccination. It is, therefore, critical to evaluate the vaccine's safety, immunogenicity, and protection efficacy during pregnancy. However, because it is affected by previous influenza vaccination or infection, the efficacy of the seasonal trivalent inactivated influenza vaccine is difficult to evaluate in pregnant women. The A/H1N1pdm pandemic in 2009 provided us with the opportunity to evaluate the immunogenicity of the influenza vaccine unaffected by previous vaccinations or infections. Vaccination with inactivated influenza virus during pregnancy elicited neutralizing antibody titers that were sufficient and comparable to those of naturally infected individuals. Furthermore, post-pandemic surveys provided a wealth of definitive information on vaccine efficacy and safety. In addition, transplacental transfer of antibodies following vaccination protected newborn infants against influenza infection. With reports showing the effectiveness of influenza vaccine during pregnancy, it is suggested that influenza vaccination benefits both mothers and their young infants.

Child, household, and caregiver characteristics associated with hospitalization for influenza among children 6-59 months of age: an emerging infections program study

BACKGROUND

Young children are at increased risk of severe outcomes from influenza illness, including hospitalization. We conducted a case-control study to identify risk factors for influenza-associated hospitalizations among children in US Emerging Infections Program sites.

METHODS

Cases were children 6-59 months of age hospitalized for laboratory-confirmed influenza infections during 2005-2008. Age- and zip-code-matched controls were enrolled. Data on child, caregiver and household characteristics were collected from parents and medical records. Conditional logistic regression was used to identify independent risk factors for hospitalization.

RESULTS

We enrolled 290 (64%) of 454 eligible cases and 1089 (49%) of 2204 eligible controls. Risk for influenza hospitalization increased with maternal age <26 years [odds ratio (OR): 1.8, 95% confidence interval (CI): 1.1-2.9]; household income below the poverty threshold (OR: 2.2, 95% CI: 1.4-3.6); smoking by >50% of household members (OR: 2.9, 95% CI: 1.4-6.6); lack of household influenza vaccination (OR: 1.8, 95% CI: 1.2-2.5) and presence of chronic illnesses, including hematologic/oncologic (OR: 11.8, 95% CI: 4.5-31.0), pulmonary (OR: 2.9, 95% CI: 1.9-4.4) and neurologic (OR: 3.8, 95% CI: 1.6-9.2) conditions. Full influenza immunization decreased the risk among children 6-23 months of age (OR: 0.5, 95% CI: 0.3-0.9) but not among those 24-59 months of age (OR: 1.5, 95% CI: 0.8-3.0; P value for difference = 0.01).

CONCLUSIONS

Chronic illnesses, young maternal age, poverty, household smoking and lack of household influenza vaccination increased the risk of influenza hospitalization. These characteristics may help providers to identify young children who are at greatest risk for severe outcomes from influenza illness.

Clinical manifestations of respiratory adenoviral infection among hospitalized children in Korea

BACKGROUND

The objective of our study was to understand the epidemiological and clinical features of respiratory adenoviral infections among children at a single institution over the course of several years.

METHODS

From January 2005 to April 2009, 1836 children (≤15 years old) who had been admitted to Korea University Ansan Hospital were tested for acute respiratory infection. The patients who were positive for an adenovirus infection were enrolled in this study, and their medical records were retrospectively reviewed.

RESULTS

Adenoviruses were isolated from 310 patients. The male to female ratio was 1.6:1 and mean age was 32 ± 24 months. Children under 5 years of age had the highest prevalence. In 2007, adenovirus infections occurred endemically throughout the year. The clinical diagnoses were primarily upper respiratory tract infections (45.4%), lower respiratory tract infections (48.1%), and neurologic disease (5.2%). Associated symptoms, signs and laboratory findings included fever (91.9%), cough (83.9%), pharyngeal injection (62.3%), rale (32.6%) and elevated C-reactive protein (93.9%). The most common radiologic findings were perihilar and peribronchial infiltrates (42.6%). Co-infections were observed in 29 cases. The mean durations of hospitalization and fever were 6.2 ± 6.5 and 4.8 ± 3.1 days, respectively. The lengths of hospitalization were similar for patients admitted for upper respiratory tract infections with severe morbidity and those admitted for lower respiratory tract infections. No children in the study died.

CONCLUSION

Our study demonstrates that respiratory adenovirus infections are an important cause of hospitalization in young children, and contribute to a significant morbidity.

Low serum 25-hydroxyvitamin D level and risk of upper respiratory tract infection in children and adolescents

Background. Vitamin D may be important for immune function. Studies to date have shown an inconsistent association between vitamin D and infection with respiratory viruses. The purpose of this study was to determine if serum 25-hydroxyvitamin D (25(OH)D) was associated with laboratory-confirmed viral respiratory tract infections (RTIs) in children.

Methods. Serum 25(OH)D levels were measured at baseline and children from Canadian Hutterite communities were followed prospectively during the respiratory virus season. Nasopharyngeal specimens were obtained if symptoms developed and infections were confirmed using polymerase chain reaction. The association between serum 25(OH)D and time to laboratory-confirmed viral RTI was evaluated using a Cox proportional hazards model.

Results. Seven hundred forty-three children aged 3–15 years were followed between 22 December 2008 and 23 June 2009. The median serum 25(OH)D level was 62.0 nmol/L (interquartile range, 51.0–74.0). A total of 229 participants (31%) developed at least 1 laboratory-confirmed viral RTI. Younger age and lower serum 25(OH)D levels were associated with increased risk of viral RTI. Serum 25(OH)D levels <75 nmol/L increased the risk of viral RTI by 50% (hazard ratio [HR], 1.51; 95% confidence interval [CI], 1.10–2.07, P = .011) and levels <50 nmol/L increased the risk by 70% (HR, 1.67; 95% CI, 1.16–2.40, P = .006).

Conclusions. Lower serum 25(OH)D levels were associated with increased risk of laboratory-confirmed viral RTI in children from Canadian Hutterite communities. Interventional studies evaluating the role of vitamin D supplementation to reduce the burden of viral RTIs are warranted.

Clinical features and outcomes of influenza A and B infections in children

The aim of the study was to describe the course of influenza among children aged 0-59 months. A total of 150 children with influenza-like symptoms (ILI): cough, fever >37.8 °C, and sore throat was included into the observation. All children were tested with both rapid influenza detection test (RIDT) BD Directigen™ EZ Flu A+B® and RT-PCR. Sixty four cases of influenza were diagnosed (incidence rate 40 %): 19 (30 %) cases of influenza caused by type B virus and 45 (70 %) cases caused by type A virus. Children with influenza required more often follow up visits (p < 0.05, OR 1.99, 95 % CI 1.03-3.85) and less often were administrated antibiotic therapy (p < 0.05, OR 0.25, 95 % CI 0.04-0.97). The logistic regression analysis revealed that only positive result of rapid influenza detection test, not any of clinical symptoms, could be found as an independent predictor of influenza (OR 4.37, 95 % CI 2.03-9.43). Patients with influenza type A more often reported muscle ache (p < 0.05) and complications (p < 0.05; OR 6.06, 95 % CI 1.20-60.38). Otitis media occurred more often among patients with than without influenza (p < 0.01; OR 15.50, 95 % CI 2.10-688.5). We conclude that although influenza infections among children younger than 59 months were generally mild and self-limited, pediatric burden of the disease was significant.

Vaccines for preventing influenza in healthy children

BACKGROUND

The consequences of influenza in children and adults are mainly absenteeism from school and work. However, the risk of complications is greatest in children and people over 65 years of age.

OBJECTIVES

To appraise all comparative studies evaluating the effects of influenza vaccines in healthy children, assess vaccine efficacy (prevention of confirmed influenza) and effectiveness (prevention of influenza-like illness (ILI)) and document adverse events associated with influenza vaccines.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 3) which includes the Acute Respiratory Infections Group's Specialised Register, OLD MEDLINE (1950 to 1965), MEDLINE (1966 to November 2011), EMBASE (1974 to November 2011), Biological Abstracts (1969 to September 2007), and Science Citation Index (1974 to September 2007).

SELECTION CRITERIA

Randomised controlled trials (RCTs), cohort and case-control studies of any influenza vaccine in healthy children under 16 years of age.

DATA COLLECTION AND ANALYSIS

Four review authors independently assessed trial quality and extracted data.

MAIN RESULTS

We included 75 studies with about 300,000 observations. We included 17 RCTs, 19 cohort studies and 11 case-control studies in the analysis of vaccine efficacy and effectiveness. Evidence from RCTs shows that six children under the age of six need to be vaccinated with live attenuated vaccine to prevent one case of influenza (infection and symptoms). We could find no usable data for those aged two years or younger.Inactivated vaccines in children aged two years or younger are not significantly more efficacious than placebo. Twenty-eight children over the age of six need to be vaccinated to prevent one case of influenza (infection and symptoms). Eight need to be vaccinated to prevent one case of influenza-like-illness (ILI). We could find no evidence of effect on secondary cases, lower respiratory tract disease, drug prescriptions, otitis media and its consequences and socioeconomic impact. We found weak single-study evidence of effect on school absenteeism by children and caring parents from work. Variability in study design and presentation of data was such that a meta-analysis of safety outcome data was not feasible. Extensive evidence of reporting bias of safety outcomes from trials of live attenuated influenza vaccines (LAIVs) impeded meaningful analysis. One specific brand of monovalent pandemic vaccine is associated with cataplexy and narcolepsy in children and there is sparse evidence of serious harms (such as febrile convulsions) in specific situations.

AUTHORS' CONCLUSIONS

Influenza vaccines are efficacious in preventing cases of influenza in children older than two years of age, but little evidence is available for children younger than two years of age. There was a difference between vaccine efficacy and effectiveness, partly due to differing datasets, settings and viral circulation patterns. No safety comparisons could be carried out, emphasising the need for standardisation of methods and presentation of vaccine safety data in future studies. In specific cases, influenza vaccines were associated with serious harms such as narcolepsy and febrile convulsions. It was surprising to find only one study of inactivated vaccine in children under two years, given current recommendations to vaccinate healthy children from six months of age in the USA, Canada, parts of Europe and Australia. If immunisation in children is to be recommended as a public health policy, large-scale studies assessing important outcomes, and directly comparing vaccine types are urgently required. The degree of scrutiny needed to identify all global cases of potential harms is beyond the resources of this review. This review includes trials funded by industry. An earlier systematic review of 274 influenza vaccine studies published up to 2007 found industry-funded studies were published in more prestigious journals and cited more than other studies independently from methodological quality and size. Studies funded from public sources were significantly less likely to report conclusions favourable to the vaccines. The review showed that reliable evidence on influenza vaccines is thin but there is evidence of widespread manipulation of conclusions and spurious notoriety of the studies. The content and conclusions of this review should be interpreted in the light of this finding.

Pandemic (H1N1) 2009 influenza in Canadian pediatric cancer and hematopoietic stem cell transplant patients

BACKGROUND

The impact of pandemic H1N1 influenza (pH1N1) virus in pediatric cancer is uncertain. The objectives of this study were to characterize the clinical course of pH1N1 and identify factors associated with severe outcomes.

METHODS

We conducted a Canadian multicenter retrospective review of children with cancer and stem cell transplant (SCT) recipients who were diagnosed with laboratory-confirmed pH1N1 infection between May 1, 2009 and January 31, 2010.

RESULTS

We identified 100 (19 in wave 1 and 81 in wave 2) cases of pH1N1 infection. Median age was 8.7 years. 71% had a hematologic malignancy, and 20% received SCT. Median duration of fever and illness was 2 and 12.5 days, respectively. 51 (51.5%) were hospitalized for a median of 5 days, with no deaths and only 1 requiring admission to the intensive care unit. Radiologically confirmed pneumonia was diagnosed in 10 (10%). Interruption of chemotherapy or conditioning occurred in 43 patients. In multivariable analyses, age <5 years (relative to ≥ 10 years) and neutropenia were associated with hospitalization while neutropenia was associated with pneumonia. Despite oseltamivir use in 89%, viral shedding was prolonged (median, 46 days) and often persisted after symptom resolution. However, an extended treatment course (>5 days) correlated with shortened duration of viral shedding (P=0.041).

CONCLUSIONS

pH1N1 infection in pediatric cancer and SCT patients infrequently caused complications but commonly interrupted cancer treatment. Persistent shedding of virus after illness resolution was common. Further research is needed to verify this finding as it could have implications for treatment guidelines and infection control practices.

Severe influenza cases in paediatric intensive care units in Germany during the pre-pandemic seasons 2005 to 2008

BACKGROUND

Data on complications in children with seasonal influenza virus infection are limited. We initiated a nation-wide three-year surveillance of children who were admitted to a paediatric intensive care unit (PICU) with severe seasonal influenza.

METHODS

From October 2005 to July 2008, active surveillance was performed using an established reporting system for rare diseases (ESPED) including all paediatric hospitals in Germany. Cases to be reported were hospitalized children < 17 years of age with laboratory-confirmed influenza treated in a PICU or dying in hospital.

RESULTS

Twenty severe influenza-associated cases were reported from 14 PICUs during three pre-pandemic influenza seasons (2005-2008). The median age of the patients (12 males/8 females) was 7.5 years (range 0.1-15 years). None had received vaccination against influenza. In 14 (70%) patients, the infection had been caused by influenza A and in five (25%) by influenza B; in one child (5%) the influenza type was not reported. Patients spent a median of 19 (IQR 12-38) days in the hospital and a median of 11 days (IQR 6-18 days) in the PICU; 10 (50%) needed mechanical ventilation. Most frequent diagnoses were influenza-associated pneumonia (60%), bronchitis/bronchiolitis (30%), encephalitis/encephalopathy (25%), secondary bacterial pneumonia (25%), and ARDS (25%). Eleven (55%) children had chronic underlying medical conditions, including 8 (40%) with chronic pulmonary diseases. Two influenza A- associated deaths were reported: i) an 8-year old boy with pneumococcal encephalopathy following influenza infection died from cerebral edema, ii) a 14-year-old boy with asthma bronchiale, cardiac malformation and Addison's disease died from cardiac and respiratory failure. For nine (45%) patients, possibly permanent sequelae were reported (3 neurological, 3 pulmonary, 3 other sequelae).

CONCLUSIONS

Influenza-associated pneumonia and secondary bacterial infections are relevant complications of seasonal influenza in Germany. The incidence of severe influenza cases in PICUs was relatively low. This may be either due to the weak to moderate seasonal influenza activity during the years 2005 to 2008 or due to under-diagnosis of influenza by physicians. Fifty% of the observed severe cases might have been prevented by following the recommendations for vaccination of risk groups in Germany.

Seasonal influenza: the burden of disease in children

During the past decade, accumulating data on the impact of influenza virus-related disease in children have become available. In this review, we summarize and discuss these data. We conclude that mortality due to influenza in children is relatively limited. But, in contrast, influenza-related hospitalizations occur frequently. The bulk of the influenza-related disease burden is experienced in the outpatient setting. This results in sometimes very high consultation rates, frequent complications, and substantial parental work absenteeism.

Comparison of pandemic and seasonal influenza in the pediatric emergency department

BACKGROUND

Emergency department (ED) presentation of pediatric pandemic H1N1 (pH1N1) infection is not well characterized. Our objective was to describe the clinical manifestations of pH1N1 in the pediatric ED. We also compared these characteristics to seasonal influenza A, and explored risk factors for pH1N1 hospitalization.

METHODS

We conducted a retrospective cohort study at a pediatric hospital in Quebec City, Canada. Subjects were ED patients aged 0 to 17 years with laboratory-confirmed pH1N1 (April-July 2009) or seasonal influenza A (June 2006-March 2009). Clinical and laboratory data were analyzed by univariate and multivariate log-binomial regression.

RESULTS

A total of 127 pH1N1 cases and 110 seasonal influenza cases were identified. pH1N1 patients were older (9.5 vs. 5.6 years; P < 0.0001) and presented more rapidly (2.8 vs. 3.5 days; P = 0.02). Clinical manifestations were similar, although gastrointestinal findings were less frequent in pH1N1 (relative risk [RR]: 0.49; 95% confidence interval [CI]: 0.37-0.65). Hospitalization risk was similar (RR: 1.12; 95% CI: 0.81-1.55), but hospitalized pH1N1 subjects were more frequently diagnosed with pneumonia (RR: 2.41; 95% CI: 1.16-5.00). In a multivariable model, age <2 years was independently associated with pH1N1 hospitalization (RR: 3.17; 95% CI: 1.78-5.65), whereas the absence of significant comorbidities decreased its risk (RR: 0.51; 95% CI: 0.31-0.85).

CONCLUSIONS

After adjustment for age and delay to presentation, clinical manifestations and 21-day outcomes of pediatric pH1N1 were similar to those of seasonal influenza. pH1N1 patients with previously established risk factors for severe seasonal influenza experienced increased hospitalization risk. Our results suggest that pH1N1 clinical diagnosis and management in the pediatric ED can be performed in a manner similar to seasonal influenza.

Influenza vaccination, diagnosis, and treatment in children

Between 2009 and 2010, the influenza H1N1 pandemic swept across the globe, disproportionately affecting the pediatric population. This pandemic strain is expected to circulate again with other seasonal influenza strains during the 2010-2011 season. This article reviews the new 2010 to 2011 Centers for Disease Control and Prevention and American Academy of Pediatrics recommendations for vaccination against the influenza virus for pediatric patients. It reviews the various testing modalities and the benefits and disadvantage of each test and offers an approach to diagnostic testing. Lastly, it reviews the indications and recommendations for treatment of children with presumed or confirmed influenza infection.

Influenza vaccination options to prevent hospitalization

BACKGROUND

Vaccination of children against influenza remains a controversial topic despite the substantial morbidity caused by this infection.

OBJECTIVE

To estimate the effect of three different vaccination strategies on preventing hospitalization due to influenza.

METHODS

A retrospective chart review was conducted of all children admitted to a tertiary health care centre who tested positive for influenza during three consecutive influenza seasons.

RESULTS

The final analysis included 208 cases with an age range of five days to 16.1 years. Seventy-six children were considered 'high-risk' and 132 were considered 'previously healthy'. Length of stay (LOS) ranged from one day to 46 days with a mean of 6.3 days. The mean LOS was 8.6 days for children with risk factors and 4.9 days for those without risk factors. The number of preventable influenza admissions was determined over three years and averaged over one year for the three vaccination strategies. A universal strategy of vaccinating all previously healthy and high-risk children over six months of age would have prevented 118 admissions. Using a selective strategy of vaccinating only children over six months of age with risk factors and a third strategy of vaccinating only two- to six-month-old infants would have prevented 58 and 55 admissions, respectively.

CLINICAL IMPLICATION

Use of the universal vaccination strategy would have prevented over one-half of the influenza admissions, which was over twice that of targeted vaccination. Until the challenges of implementing universal vaccination are fully understood, targeted vaccination remains an acceptable alternative.

Admission diagnoses of children 0-16 years of age hospitalized with influenza

The prompt diagnosis of influenza enables the institution of antiviral therapy and adequate cohorting of patients, but scarce data are available to help clinicians correctly suspect influenza in children at the time of admission. This 16-year retrospective study assessed the main admission diagnoses of 401 children aged ≤16 years hospitalized with virologically confirmed influenza. The clinical data were derived from a systematic review of the medical records of the children. Sepsis-like illness was the main reason for admission in 52% of infants aged <6 months and in 7-16% of the older children. Respiratory symptoms accounted for 38% of admissions, and 15% of children were hospitalized due to acute neurologic conditions, primarily febrile convulsions. Wheezing or exacerbation of asthma was the primary reason for admission in 14% of children aged <3 years. No differences were observed in the admission diagnoses between children with influenza A and B infections. The main admission diagnoses vary widely in different age groups of children with influenza, and only a minority of children are hospitalized for respiratory symptoms. The leading role of sepsis-like illness in infants aged <6 months calls for increased efforts to find protective measures against influenza in this age group.

Gender specific differences in the immune response to infection

There are many instances where males and females differ in the susceptibility to infections. The reason for these differences in susceptibility is multifactorial. The primary cause is thought to be due to differences induced by sex hormones and their effects on gene expression as well as the immune system, but may also be due to innate physiological differences between males and females. This review summarizes gender specific differences seen in infections caused by bacteria, fungi, parasites and viruses. Ultimately, gender specific differences appear to be dependent on the microbe causing the infection, as not every infection with a specific microbial type results in increased susceptibility of one gender over the other. This suggests that there is an interaction between gender specific immune differences and the specific immune response to individual microbes.

Novel influenza A (H1N1): clinical features of pediatric hospitalizations in two successive waves

OBJECTIVE

To describe and compare the characteristics of children hospitalized with novel influenza A (H1N1) during two successive waves.

METHODS

This was a medical chart review of all children hospitalized in a French Canadian pediatric hospital in Montreal in the spring and fall of 2009 with a positive real-time polymerase chain reaction for novel influenza A (H1N1) and flu-like symptoms.

RESULTS

We included 202 children with a median age of 4.9 (range 0.1-18) years. Demographic and clinical features of the children in the two waves were similar. One or more underlying medical conditions were found in 59% of the children. Clinical findings at admission were: fever (98%), cough (88%), congestion/rhinorrhea (58%), gastrointestinal symptoms (47%), oxygen saturation below 95% (33%), sore throat (20%), and neurological symptoms (9%). Admission to the intensive care unit was required for 22 (11%) children, and 14 patients needed respiratory support. During the second wave, the median duration of stay was shorter (3 vs. 4 days, p=0.003) and oseltamivir was used more often (84% vs. 40%, p<0.001).

CONCLUSIONS

Children hospitalized during the two successive waves of H1N1 were mainly school-aged and suffered from moderate disease. Although clinical features and severity of disease were similar, oseltamivir was prescribed more frequently and the length of hospital stay was shorter in the second wave.

Estrogens augment cell surface TLR4 expression on murine macrophages and regulate sepsis susceptibility in vivo

Gender-based differences exist in infectious disease susceptibility. In general, females generate more robust and potentially protective humoral and cell-mediated immune responses after antigenic challenge than their male counterparts. Furthermore, evidence is accumulating that sex may also influence the early perception of microbial challenges and the generation of inflammatory immune responses such as sepsis. These differences have previously been attributed to the actions of reproductive hormones. Whereas androgens have been shown to suppress acute host immune responses to bacterial endotoxin challenge, estrogens have been found to promote increased resistance to bacterial infections. However, the mechanisms by which estrogens exert immunoprotective effects have not been established. In this study, we investigated the in vivo effects of 17beta-estradiol on endotoxin susceptibility in mice. Importantly, we have examined the actions of this female reproductive hormone on the expression of pattern recognition receptors that recognize bacterial endotoxin by key innate immune sentinel cells. We show that removal of endogenous estrogens decreases both pro- and antiinflammatory cytokine production, with a concomitant reduction in circulating levels of lipopolysaccharide-binding protein and cell surface expression of Toll-like receptor 4 on murine macrophages. Exogenous in vivo replacement of 17beta-estradiol, but not progesterone, significantly elevates sera lipopolysaccharide-binding protein levels and cell surface expression of Toll-like receptor 4 and CD14 on macrophages. Furthermore, this effect corresponds with significantly higher inflammatory cytokine levels after in vivo lipopolysaccharide challenge and a marked increase in endotoxin-associated morbidity. Taken together, these data provide a potential mechanism underlying the immunoenhancing effects of estrogens.

Effects of oseltamivir on influenza-related complications in children with chronic medical conditions

OBJECTIVE

This study investigated the influence of oseltamivir on influenza-related complications and hospitalizations for children and adolescents, 1 to 17 years of age, with chronic medical conditions or neurologic or neuromuscular disease.

METHODS

In a retrospective study, outcomes for patients who were given oseltamivir within 1 day after influenza diagnosis were compared with those for patients who received no antiviral therapy. Anonymous data from MarketScan databases (Thomson Reuters, Cambridge, MA) were used to identify patients from 6 influenza seasons between 2000 and 2006. The study outcomes were frequencies of pneumonia, respiratory illnesses other than pneumonia, otitis media, and hospitalization.

RESULTS

Oseltamivir was prescribed for 1634 patients according to the study criteria, and 3721 patients received no antiviral therapy for their influenza. After adjustment for demographic and medical history variables, oseltamivir was associated with significant reductions in the risks of respiratory illnesses other than pneumonia, otitis media and its complications, and all-cause hospitalization in the 14 days after influenza diagnosis. Analyses for 30 days after influenza diagnosis also showed significant risk reductions for respiratory illnesses other than pneumonia, otitis media and its complications, and all-cause hospitalization with oseltamivir.

CONCLUSION

When it was prescribed at influenza diagnosis, oseltamivir was associated with reduced risks of influenza-related complications and hospitalizations for children and adolescents at high risk of influenza complications.

Immune dysregulation in severe influenza

Among previously healthy children with severe influenza, the mechanisms leading to increased pathology are not understood. We hypothesized that children with severe influenza would have high levels of circulating cytokines. To examine this, we recruited patients with severe influenza and examined plasma cytokine levels as well as the ability of peripheral blood cells to respond to stimuli. Ten patients with severe influenza were enrolled during the 2005-2007 influenza seasons. We evaluated plasma cytokine levels, circulating NK cells, and responses to TLR ligands during the illness. We compared these patients with five patients with moderate influenza, six patients with respiratory syncytial virus (RSV), and 24 noninfected controls. Patients with influenza showed depressed responses to TLR ligands when compared with RSV patients and healthy controls (P<0.05). These normalized when retested during a convalescent phase. Plasma levels of IL-6, IL-12, and IFN- were elevated in influenza patients compared with controls (P<0.05). A compromised ability to produce TNF- was reproduced by in vitro infection, and the magnitude of the effect correlated with the multiplicity of infection and induction of IFN regulatory factor 4 expression. Aberrant, systemic, innate responses to TLR ligands during influenza infection may be a consequence of specific viral attributes such as a high inoculum or rapid replication and may underlie the known susceptibility of influenza-infected patients to secondary bacterial infections.

Influenza-associated hospitalization in urban Thai children

BACKGROUND

Studies in North America and Europe have shown that young children are at increased risk of serious complications and hospitalization from influenza infection. In Thailand, however, influenza is commonly considered a mild infection that rarely requires hospitalization. An improved understanding of the burden of serious complications from influenza infection in young children is needed to inform clinical treatment and vaccination guidelines.

METHODS

We conducted a prospective study of children 0-5 years of age with lower respiratory tract infection or influenza-like illness admitted to a pediatric tertiary-care hospital in Bangkok, Thailand during July 2004 to July 2005. All respiratory specimens were tested for influenza using a rapid antigen test and tissue cell culture.

RESULTS

Thirty-nine of 456 (8.6%) hospitalized children had culture-positive influenza. Eighty percent of hospitalized influenza patients had no underlying chronic illnesses. Nineteen (49%) influenza patients required hospital stays of 5 days or more and two patients required mechanical ventilation. Influenza activity demonstrated bimodal seasonal variation with peak activity from August to October and January to April. Cough was present in 38 (97%) cases and fever >38.5 degrees C was significantly associated with influenza.

CONCLUSION

Influenza is an important cause of hospitalization in children <5 years of age in Thailand. Children <5 years should be considered as a target group when establishing clinical guidelines for antiviral treatment and influenza vaccination.

Development and validation of a risk score for predicting hospitalization in children with influenza virus infection

OBJECTIVE

Influenza virus infections cause significant morbidity and often result in hospitalization in children. Many children with influenza seek care in emergency settings during seasonal influenza epidemics. We hypothesized that certain features could predict the need for hospitalization in children with influenza.

METHODS

Retrospective cohort study of all children 18 years or younger seen at a children's hospital with laboratory-confirmed influenza infection between July 2001 and June 2004. Medical records of children with confirmed influenza virus infection were reviewed. Predictors of admission were identified using logistic regression models. An influenza risk score system was created and validated based on 4 predictors.

RESULTS

We identified 1230 children with laboratory proven influenza virus infection, 541 were hospitalized. Multivariate logistic regression demonstrated that 4 predictors were independently strongly associated with hospitalization. In the clinical prediction rule for children with influenza who were hospitalized, history of a high-risk medical condition (odds ratio [OR], 4.06; 95% confidence interval [CI], 2.91-5.68) was worth 2 points. Respiratory distress on physical examination (OR, 2.33; 95% CI, 1.61-3.38) was worth 1 point. Radiographic evidence of focal pneumonia (OR, 7.82; 95% CI, 3.62-16.92) was worth 3 points and influenza B infection (OR, 3.99; 95% CI, 2.57-6.21) was worth 2 points. High-risk children with influenza with a total risk score of 3 to 8 had an 86% probability of hospitalization.

CONCLUSIONS

The presence of a high-risk medical condition, respiratory distress on physical examination, radiographic evidence of focal pneumonia, and influenza B infection were the 4 strongest predictors of hospitalization. The risk score assigned to a child with influenza may provide a disposition tool for predicting hospitalization in children in seasonal influenza epidemics.

Seasonal influenza in adults and children--diagnosis, treatment, chemoprophylaxis, and institutional outbreak management: clinical practice guidelines of the Infectious Diseases Society of America

Guidelines for the treatment of persons with influenza virus infection were prepared by an Expert Panel of the Infectious Diseases Society of America. The evidence-based guidelines encompass diagnostic issues, treatment and chemoprophylaxis with antiviral medications, and issues related to institutional outbreak management for seasonal (interpandemic) influenza. They are intended for use by physicians in all medical specialties with direct patient care, because influenza virus infection is common in communities during influenza season and may be encountered by practitioners caring for a wide variety of patients.

Clinical and laboratory analysis of influenza B infection in children in Taichung, Taiwan during the 2006-2007 flu season

BACKGROUND

An epidemic of influenza B/Malaysia/2506/2004 was reported in Taiwan during the 2006-2007 flu season. We investigated the flu vaccination history and clinical and Laboratory characteristics of children with influenza B infection.

METHODS

We enrolled children younger than 18 years old who visited one of two hospitals between November 2006 and February 2007 with influenza-like illnesses. Throat swabs were taken on their first visit and cultured for viruses. Complete and differential blood counts and blood biochemical parameters were analyzed in some children.

RESULTS

Influenza virus was cultured from 51.0% of patients (101/198), 87 (86.1%) of who were infected with influenza virus type B. The remaining 14 (13.9%) were infected with influenza virus type AH3. The 87 children (median age 7.8 years) with culture-proven influenza B virus infection were enrolled. Nine parents reported that enrolled children had been vaccinated against influenza. Leukopenia was found in 56.1% (32/57) of patients, leukocytosis in 3.5% (2/57), and thrombocytopenia in 1.8% (1/57). Thirteen of 23 patients (56%) tested for creatine kinase (CK) had elevated levels ( >160 U/L), and 11 of 23 (47.8%) had myalgia associated with raised CK (p < 0.05). Twenty-six children developed complications, including one case of pneumonia with acute respiratory distress syndrome and one case of flu-associated encephalitis.

CONCLUSION

Most children who contracted influenza B infection had not been vaccinated. Almost half the children had leukopenia, and some had leukocytosis, but thrombocytopenia was rare. There was a significant association between raised CK levels and myalgia in influenza B infection.

The safety and immunogenicity of influenza vaccine in children with asthma in Mexico

BACKGROUND

The morbidity and mortality associated with influenza is substantial in children with asthma. There are no available data on the safety and immunogenicity of influenza vaccine in children with asthma in Latin America. Furthermore, it is unclear if influenza vaccination may cause asthma exacerbations.

METHODS

We conducted a placebo-controlled trial to investigate the safety and immunogenicity of an inactivated trivalent split virus influenza vaccine in children with asthma in Mexico. We also measured the impact of influenza vaccination on pulmonary function tests in this population.

RESULTS

The inactivated influenza vaccine was immunogenic and safe in terms of local and systemic side effects compared to placebo. We observed no significant impact on pulmonary function tests among vaccine recipients.

CONCLUSIONS

Given the significant morbidity associated with influenza in children, strategies to promote increased influenza vaccination coverage in this high-risk group in Latin America and elsewhere are urgently needed.

Control of an outbreak due to an adamantane-resistant strain of influenza A (H3N2) in a chronic care facility

BACKGROUND

Chronic care facility residents are at risk of severe influenza infection and death. Adamantanes have been used by chronic care facilities for influenza A prophylaxis; however, genotypic resistance has altered prophylaxis recommendations. An outbreak of influenza A (H3N2) in a chronic care facility housing neurologically impaired children and young adults and subsequent control measures are described.

PATIENTS AND METHODS

Resident charts were retrospectively reviewed. Isolates were characterized by strain identification and pyrosequencing.

RESULTS

Although 95 (97%) of 98 residents had been immunized against influenza at the start of the influenza season, 16 (84%) of 19 case patients were identified on the first floor. However, following implementation of enhanced infection control practices and adamantane prophylaxis, only 10 (13%) of 79 case patients were identified on the second floor. Subsequent pyrosequencing studies revealed a serine to asparagine mutation at position 31 of the M2 protein.

CONCLUSIONS

Enhanced infection control precautions and adamantane prophylaxis were used to control spread of influenza in a chronic care facility. This outbreak demonstrates the importance of timely and consistent implementation of infection control measures in controlling influenza outbreaks in long term care facilities and raises questions about a possible role for adamantanes in preventing transmission of adamantane-resistant influenza A viruses.

Vaccines for preventing influenza in healthy children

BACKGROUND

The consequences of influenza in children and adults are mainly absenteeism from school and work. However, the risk of complications is greatest in children and people over 65 years old.

OBJECTIVES

To appraise all comparative studies evaluating the effects of influenza vaccines in healthy children; assess vaccine efficacy (prevention of confirmed influenza) and effectiveness (prevention of influenza-like illness) and document adverse events associated with influenza vaccines.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2007, issue 3); OLD MEDLINE (1950 to 1965); MEDLINE (1966 to September 2007); EMBASE (1974 to September 2007); Biological Abstracts (1969 to September 2007); and Science Citation Index (1974 to September 2007).

SELECTION CRITERIA

Randomised controlled trials (RCTs), cohort and case-control studies of any influenza vaccine in healthy children under 16 years of age.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data.

MAIN RESULTS

Fifty-one studies with 294,159 observations were included. Sixteen RCTs and 18 cohort studies were included in the analysis of vaccine efficacy and effectiveness. From RCTs, live vaccines showed an efficacy of 82% (95% confidence interval (CI) 71% to 89%) and an effectiveness of 33% (95% CI 28% to 38%) in children older than two compared with placebo or no intervention. Inactivated vaccines had a lower efficacy of 59% (95% CI 41% to 71%) than live vaccines but similar effectiveness: 36% (95% CI 24% to 46%). In children under two, the efficacy of inactivated vaccine was similar to placebo. Variability in study design and presentation of data was such that a meta-analysis of safety outcome data was not feasible. Extensive evidence of reporting bias of safety outcomes from trials of live attenuated vaccines impeded meaningful analysis.

AUTHORS' CONCLUSIONS

Influenza vaccines are efficacious in children older than two but little evidence is available for children under two. There was a marked difference between vaccine efficacy and effectiveness. No safety comparisons could be carried out, emphasizing the need for standardisation of methods and presentation of vaccine safety data in future studies. It was surprising to find only one study of inactivated vaccine in children under two years, given current recommendations to vaccinate healthy children from six months old in the USA and Canada. If immunisation in children is to be recommended as a public health policy, large-scale studies assessing important outcomes and directly comparing vaccine types are urgently required.

Safety and tolerability of cold-adapted influenza vaccine, trivalent, in infants younger than 6 months of age

OBJECTIVE

Young children are at high risk for influenza-related complications. Vaccination of close household contacts is recommended to provide indirect protection to children <6 months of age. Studies have shown that live, cold-adapted influenza vaccine, trivalent, is efficacious in children. To assess the risks associated with inadvertent exposure of infants to vaccine viruses from vaccinated contacts, this study was designed to evaluate the safety and tolerability of cold-adapted influenza vaccine, trivalent, administered intranasally to healthy children 6 to <24 weeks of age.

METHODS

Healthy infants aged 6 to <16 weeks and 16 to <24 weeks, respectively, were randomly assigned to receive 2 doses of influenza vaccine, or placebo intranasally 35 +/- 7 days apart. Reactogenicity events were monitored for 11 days after each dose. Other adverse events were monitored through 28 to 35 days after dose 2.

RESULTS

Of the infants aged 6 to <16 weeks, 31 received influenza vaccine and 28 received placebo, and of those aged 16 to <24 weeks, 30 received influenza vaccine and 31 received placebo. In the 6- to <16-week cohort, more influenza vaccine, recipients experienced irritability (66.7% vs 35.7%) and runny nose or nasal congestion (63.3% vs 33.3%) after dose 1 but not dose 2. There were no significant increases in any other reactogenicity events or adverse events in the vaccine recipients compared with the placebo group.

CONCLUSIONS

Although there was an increase in mild reactogenicity events in children 6 to <16 weeks of age, cold-adapted influenza vaccine, trivalent, was generally well tolerated in infants 6 to <24 weeks of age. These findings support further evaluation of cold-adapted influenza vaccine, trivalent, in infants <6 months of age.