The burden of influenza in children

The Safety and Immunogenicity of a Quadrivalent Influenza Subunit Vaccine in Healthy Children Aged 6-35 Months: A Randomized, Blinded and Positive-Controlled Phase III Clinical Trial

Background: Influenza is a serious contagious disease caused by influenza virus. It is particularly dangerous for children, potentially leading to severe and even fatal complications. The aim of this study was to evaluate the safety and immunogenicity of two candidate quadrivalent influenza subunit vaccines in children aged 6-35 months. Methods: The subjects were randomly divided into three groups at a 1:1:1 ratio and received the corresponding vaccines: QIV-Sub-HD (Quadrivalent Influenza Subunit Vaccine, High Dose), QIV-Sub-LD (Quadrivalent Influenza Subunit Vaccine, Low Dose) and QIV-Split-LD (Quadrivalent Influenza Split-Virion Vaccine, Low Dose). Adverse events were recorded at 30 min, 0-7 days and 8-28 and 30 days after each dose of immunization. Serious adverse events (SAEs) were collected and reported within 6 months after the full vaccination. Blood samples were collected before the first dose and on 28 days, 3 months and 6 months after full vaccination for antibody detection to evaluate the immunogenicity and duration of immune responses. Results: The results showed that the relative and absolute criteria met the goals set by the clinical trial protocol, indicating that both vaccines are immunogenic. From the first dose to 30 days after full vaccination, the total incidence of adverse reactions in the QIV-Sub-HD, QIV-Sub-LD and QIV-Split-LD groups was 29.64%, 33.33% and 29.64%, respectively. The main symptoms were fever, cough, diarrhea and vomiting. No new safety concerns were identified. Conclusions: The quadrivalent influenza subunit vaccines candidate, manufactured by Ab&B Bio-tech Co., Ltd. JS., are safe and immunogenic in children aged 6-35 months.

Profiling lipid mediators in serum from children with H1N1 influenza

Influenza A virus subtype H1N1 can cause severe acute respiratory distress syndrome and death in young children and elderly individuals. H1N1 initiates inflammatory responses that aim to contain and eliminate microbial invaders. Various lipid mediators (LMs) are biosynthesized and play a critical role in fighting viruses during inflammation; thus, by profiling the LMs in patients, researchers can obtain mechanistic insights into diseases, such as the pathways disrupted. To date, the relationship between molecular alterations in LMs and the pathogenesis of H1N1 influenza in children is poorly understood. Here, we employed a targeted liquid chromatography coupled with tandem mass spectrometry (LC‒MS/MS) to profile LMs in serum from children with H1N1 influenza (H1N1 children) and recovered children. We found that 22 LM species were altered in H1N1 children with mild symptoms. Analysis of the LM profiles of recovered children revealed a decrease in the levels of thromboxane B2 (TxB2) and thromboxane B3 (TxB3) and an increase in the levels of other 8 altered LM species associated with H1N1 influenza, including cytochrome P450 (CYP) enzyme-derived dihydroxyeicosatrienoic acids (DiHETrEs) and hydroxyeicosatetraenoic acids (HETEs) from arachidonic acid (AA), and epoxyoctadecamonoenoic acids (EpOMEs) from linoleic acid (LA). Taken together, the results of this study revealed that serum LMs change dynamically in H1N1 children with mild symptoms. The dramatically altered LMs in H1N1 children could serve as a basis for potential therapeutics or adjuvants against H1N1 influenza.

Immunogenicity and safety of quadrivalent inactivated influenza vaccine in children aged 6 to 35 months: A systematic review and meta-analysis

Evidence of the immunogenicity and safety of quadrivalent inactivated influenza vaccine in children aged 6 to 35 months has been emerging. To evaluate the immunogenicity and safety of quadrivalent inactivated influenza vaccine in children aged 6 to 35 months in a systematic review and meta-analysis. This meta-analysis included 12 studies with 6722 participants receiving QIV, 3575 participants receiving TIV, 4249 participants receiving full-dose QIV (F-QIV), and 3722 participants receiving half-dose QIV (H-QIV). Among children aged 6 to 35 months, QIV produces a better Immunogenicity against influenza B vaccine strains not contained in TIV. However, injection site reaction was more common for QIV, F-QIV showed superior efficacy for the B lineage, but fever and injection site pain was more frequently reported for F-QIV than H-QIV. These data support the immunogenicity and safety of quadrivalent inactivated influenza vaccine among children aged 6 to 35 months.

Caregiver Quality of Life During Pediatric Influenza-Like Illness: A Cross-Sectional Study During the COVID-19 Pandemic

The objective of this study was to quantify the quality of life (QoL) of caregivers with children with influenza-like illnesses (ILI) and to identify factors associated with worse QoL. This was a cross-sectional cohort study of caregivers in a pediatric emergency department with previously healthy young children with ILI. The primary outcome was caregiver QoL. Additional measures included health literacy, social support, and caregiver health status. Two hundred and eighty-one caregivers completed the study. And 41% reported overall QoL was worse during their child's illness. The median QoL score was 3.8 [3.1, 4.6] in a 7-point scale. Illness duration was associated with worse overall QoL score (0.128 worse for each additional day of illness). The median emotions domain score was 2.5 [1.5, 4.0], the worst of any domain. Caregivers who perceived worse illness severity had lower emotions domain scores (2.61 vs 6.00, P = .0269). Caregivers with adequate literacy had lower mean QoL scores (3.08 vs 4.44, P < .0001). Childhood illnesses worsen caregiver QoL. Factors associated with worse QoL were perception of illness severity and duration. Addressing caregiver QoL could mitigate the impact of childhood acute illnesses on caregiver wellbeing.

Pharmacist-Administered Influenza Vaccination in Children and Corresponding Regulations

In our retrospective cohort study, we evaluated trends in pharmacist-administered pediatric influenza vaccination rates in the United States and corresponding state-level pharmacist pediatric vaccination authorization models, including minimum age requirements, vaccination protocols, and/or prescription requirements. An administrative health claims database was used to capture influenza vaccinations in children less than 18 years old with 1 year of continuous enrollment and joinpoint regression was used to assess trends. Of the 3,937,376 pediatric influenza vaccinations identified over the study period, only 3.2% were pharmacist-administered (87.7% pediatrician offices, 2.3% convenience care clinics, 0.8% emergency care, and 6.0% other locations). Pharmacist-administered pediatric influenza vaccination was more commonly observed in older children (mean age 12.65 ± 3.26 years) and increased significantly by 19.2% annually over the study period (95% confidence interval 9.2%-30.2%, p < 0.05). The Northeast, with more restrictive authorization models, represented only 2.2% (n = 2816) of all pharmacist-administered pediatric influenza vaccinations. Utilization of pharmacist-administered pediatric influenza vaccination remains low. Providing children with greater access to vaccination with less restrictions may increase overall vaccination rates. Due to the COVID-19 pandemic and the Public Readiness and Emergency Preparedness Act, pharmacists will play a major role in vaccinating children.

Seasonal influenza in children: Costs for the health system and society in Europe

Background

Methods

Results

Conclusion

The Role of Type I IFNs in Influenza: Antiviral Superheroes or Immunopathogenic Villains?

The important role of interferons (IFNs) in antiviral innate immune defense is well established. Although recombinant IFN-α was approved for cancer and chronic viral infection treatment by regulatory agencies in many countries starting in 1986, no IFNs are approved for treatment of influenza A virus (IAV) infection. This is partially due to the complex effects of IFNs in acute influenza infection. IAV attacks the human respiratory system and causes significant morbidity and mortality globally. During influenza infection, depending on the strain of IAV and the individual host, type I IFNs can have protective antiviral effects or can contribute to immunopathology. In the context of virus infection, the immune system has complicated mechanisms regulating the expression and effects of type I IFN to maximize the antiviral response by both activating and enhancing beneficial innate cell function, while limiting immunopathological responses that lead to exaggerated tissue damage. In this review, we summarize the complicated, but important, role of type I IFNs in influenza infections. This includes both protective and harmful effects of these important cytokines during infection.

Incidence of Influenza Among Childhood Cancer Survivors in South Korea: A Population-based Retrospective Analysis

BACKGROUND/AIM

We quantified the incidence, and identified risk factors for influenza infection among childhood cancer survivors in South Korea, an at-risk population.

PATIENTS AND METHODS

Nationwide health insurance claims data were used to assess the frequency of influenza among childhood cancer survivors (aged <20 years) diagnosed between January 2009 and April 2016. A multivariable logistic regression was constructed to identify risk factors for influenza.

RESULTS

Of 6,457 children cancer survivors, 1,704 (27.0%) were diagnosed with influenza. Influenza was common in children <5 years old and infections were highest between late October and April. Over 60% of influenza treatment claims came from private clinics. Risk factors for influenza included age <9 years.

CONCLUSION

Childhood cancer survivors are particularly at-risk for influenza infection during the traditional influenza season. Identifying risks for influenza infection will help to establish countermeasures for reducing the influenza infections in at-risk cancer surviving children.

Safety and Immunogenicity of a Full-dose, Split-virion, Inactivated, Quadrivalent Influenza Vaccine in Healthy Children 6-35 Months of Age: A Randomized Controlled Clinical Trial

BACKGROUND

For children <3 years of age, a half dose of inactivated influenza vaccine (7.5 μg hemagglutinin per strain) has been used for more than 30 years, but several studies indicate that a full dose (15 μg hemagglutinin per strain) can be used in this population without increasing the rate of fever or other reactions. Here, we compare the safety and immunogenicity of full and half doses of quadrivalent, split-virion, inactivated influenza vaccine (IIV4) in children 6-35 months of age.

METHODS

In this phase IV, randomized, observer-blinded, multi-center study, healthy children 6-35 months of age were randomized 1:1 to be vaccinated with a half or full dose of IIV4 (NCT02915302). The primary objective was to demonstrate that the rate of any fever (≥38.0°C) up to 7 days after a full dose of IIV4 was noninferior to the rate of fever after a half dose.

RESULTS

The study included 1950 children. Noninferiority in the rate of fever was demonstrated for the full dose versus the half dose of IIV4 (difference in rate = 0.84%; 95% confidence interval, -2.13% to 3.80%). Solicited reactions and unsolicited adverse events were similar between the dose groups. No vaccine-related serious adverse events were reported. Noninferiority of both hemagglutination inhibition geometric mean titers and seroconversion rates was demonstrated for all 4 vaccine strains for the full dose versus the half dose.

CONCLUSIONS

In children 6-35 months of age, a full dose of IIV4 was immunogenic and had a safety profile comparable to that of a half dose, with no new safety concerns observed.

Influenza-associated paediatric respiratory hospitalizations in China, 1996-2012: a systematic analysis

Background

The World Health Organization recommends that children aged ≥ 6 months be vaccinated against influenza. Influenza vaccination policies depend on the evidence of the burden of influenza, yet few national data on influenza-associated severe outcomes among children exist in China.

Methods

We conducted a systematic review of articles published from 1996 to 2012 on laboratory-confirmed, influenza-associated paediatric respiratory hospitalizations in China. We extracted data and stratified the percentage of samples testing positive for influenza by age group (< 2, < 5 and < 18 years old); case definition; test methods; and geographic location. The pooled percentage of samples testing positive for influenza was estimated with a random effects regression model.

Results

Influenza was associated with 8.8% of respiratory hospitalizations among children aged < 18 years, ranging from 7.0% (95% confidence interval: 4.2–9.8%) in children aged < 2 years to 8.9% (95% confidence interval: 6.8–11%) in children aged < 5 years. The percentage of samples testing positive for influenza was consistently higher among studies with data from children aged < 5 years and < 18 years than those restricted only to children aged < 2 years; the percentages were higher in Northern China than Southern China.

Discussion

Influenza is an important cause of paediatric respiratory hospitalizations in China. Influenza vaccination of school-aged children could prevent substantial influenza-associated illness, including hospitalizations, in China.

Subtype-specific Clinical Presentation, Medical Treatment and Family Impact of Influenza in Children 1-5 Years of Age Treated in Outpatient Practices in Germany During Three Postpandemic Years, 2013-2015

BACKGROUND

Limited data on the influenza burden in pediatric outpatients are available, especially regarding direct comparison of the cocirculating (sub)types A(H1N1)pdm09, A(H3N2) and B.

METHODS

Children 1-5 years of age, unvaccinated against influenza and presenting with febrile acute respiratory infections (ARIs), were enrolled in 33 pediatric practices in Germany from 2013 to 2015 (January-May). Influenza was confirmed by multiplex polymerase chain reaction from pharyngeal swabs and (sub)typed.

RESULTS

In 805 children with ARI, influenza was the most frequently detected respiratory virus (n = 305; 37.9%). Of 217 influenza patients included, 122 (56.2%) were infected with A(H3N2), 56 (25.8%) with A(H1N1)pdm09 and 39 (18.0%) with B. Median age was 3.7 years [interquartile range (IQR), 2.1-4.8]; 11% had underlying conditions. Median fever duration was 4 days (IQR, 3-5), and the disease duration was 9 days (IQR, 7-12). Most frequent diagnoses were pharyngitis (26%), bronchitis (18%) and acute otitis media (10%). Children received mainly antipyretics (86%) and adrenergic nasal drops/spray (53%); 9% received antibiotics and 3% oseltamivir. Thirty-six percent required at least 1 additional practice visit; 1% was hospitalized. Median absences from childcare were 5 days (IQR, 3-7); parents lost 4 workdays (IQR, 2-6). Symptoms, severity and impact on the family were largely unrelated to (sub)type. However, patients with A(H1N1)pdm09 had fewer underlying conditions (P = 0.017), whereas patients with B more often had pharyngitis (P = 0.022), acute otitis media (P = 0.012) and stenosing laryngotracheitis (P = 0.007).

CONCLUSIONS

Influenza was the most frequently detected viral pathogen in outpatient children with febrile, mostly uncomplicated ARI. In this setting, clinical manifestations and severity were similar across the (sub)types prevalent during the postpandemic seasons.

The impact of respiratory viruses on lung health after preterm birth

Children born preterm, less than 37 weeks' gestation, are at increased risk of viral respiratory infections and associated complications both during their initial birth hospitalisation and in their first years following discharge. This increased burden of viral respiratory infections is likely to have long term implications for lung health and function in individuals born preterm, particularly those with bronchopulmonary dysplasia. Several hypotheses have been put forward to explain the association between early life viral respiratory infection and development of suboptimal lung health and function later in life following preterm birth. Although preterm infants with diminished lung function, particularly small airways, might be particularly susceptible to asthma and wheezing disorders following viral infection, there is evidence that respiratory viruses can activate number of inflammatory and airway re-modelling pathways. Therefore, the aim of this review is to highlight the perinatal and early life risk factors that may contribute to increased susceptibility to viral respiratory infections among preterm infants during early life and to understand how respiratory viral infection may influence the development of abnormal lung health and function later in life.

Enhanced T helper 1 and 2 cytokine responses at birth associate with lower risk of middle ear infections in infancy

BACKGROUND

Respiratory tract infections and their symptoms are frequent during early childhood, but their risk factors, including the effect of early immune regulation, are less known. The aim of the study was to analyze whether stimulated cord blood cytokine production is associated with the frequency of respiratory tract infection symptoms or infections during the first year of life.

METHODS

The study population consisted of children of mothers from farm or non-farm rural environment from Austria, Finland, Germany, and Switzerland who participated in a prospective birth cohort study (PASTURE: Protection against Allergy-Study in Rural Environments) (N = 550). Cord blood samples were stimulated with the combination of phorbol ester and ionomycin (P/I) for 24 h, and the production of IL-5, IL-10, TNF-α, and IFN-γ was determined using ELISA. Information about infectious morbidity was collected using weekly diaries.

RESULTS

P/I-stimulated production of IL-5 (adjusted risk ratio (aRR) for ≤median production, 0.37; 95% confidence interval (CI), 0.25-0.55, aRR for >median production, 0.41; 95% CI, 0.27-0.61 vs. production <detection limit) and IFN-γ (aRR for ≤median production, 0.62; 95% CI, 0.40-0.95, aRR for >median production, 0.39; 95% CI, 0.25-0.62 vs. production <detection limit) in cord blood were associated with lower number of weeks with reported middle ear infection. There was a tendency toward positive association with P/I-stimulated TNF-α production and middle ear infections.

CONCLUSION

Our results suggest that increased Th2- and Th1-associated cytokine responses at birth may provide protection from later middle ear infections.

Influenza vaccine efficacy in young children attending childcare: A randomised controlled trial

AIM

Influenza causes a substantial burden in young children. Vaccine efficacy (VE) data are limited in this age group. We examined trivalent influenza vaccine (TIV) efficacy and safety in young children attending childcare.

METHODS

A double-blind, randomised controlled trial in children aged 6 to <48 months was conducted with recruitment from Sydney childcare centres in 2011. Children were randomised to receive two doses of TIV or control hepatitis A vaccine. Efficacy was evaluated against polymerase chain reaction-confirmed influenza using parent-collected nose/throat swabs during influenza-like-illness. Safety outcomes were assessed during 6 months of follow-up.

RESULTS

Fifty-seven children were allocated to influenza vaccine and 67 to control; all completed the study. The influenza attack rate was 1.8 vs 13.4% in the TIV and control groups, respectively; VE 87% (95%CI: 0-98%). For children aged 24 to <48 months, 0 vs 8 (18.6%) influenza infections occurred in the TIV and control groups respectively, giving a VE of 100% (16-100%). Efficacy was not shown in children 6 to <24 months, probably due to insufficient power. Injection site and systemic adverse events were mostly mild to moderate with no significant differences, apart from more mild diarrhoea following dose 2 in TIV recipients (11.8 vs 0%).

CONCLUSIONS

Influenza vaccine appeared efficacious in the subgroup of children aged 24 to <48 months, although caution is required due to the small number of participants. There were no serious adverse events and most parents would vaccinate again. Influenza vaccination in a childcare setting could be valuable and a larger confirmatory study would be helpful.

Retrospective review of factors associated with severe hospitalised community-acquired influenza in a tertiary paediatric hospital in South Australia

Background

Influenza infection can result in severe disease with debilitating complications. Young children have the highest rate of influenza hospitalisations with various factors influencing influenza susceptibility and severity.

Objectives

This study aimed to determine the disease burden and assess risk factors for severe hospitalised influenza in South Australian children under 5 years of age.

Methods

Influenza admissions to the tertiary paediatric hospital in South Australia from 2008 to 2012 were identified. Data from laboratory‐confirmed influenza cases were collected, including infecting influenza strain, co‐infections, prematurity, pre‐existing medical comorbidities and other potential risk factors. Predictors of high‐level care were assessed using logistic regression.

Results

A total of 267 children with laboratory‐confirmed influenza were hospitalised. Of these, 147 admissions (53%) occurred in children without underlying medical risk factors. Eighteen children (7%) required high‐level care, of which 11 (61%) had no underlying medical risk factors. No deaths were reported. The majority of children were unimmunised against influenza. Co‐infections were identified in 40% of children (n = 107). Influenza B was associated with a requirement for higher care (OR 3.7, CI 1.3–10.9, P = .02) as was a history of food allergies (OR 9.7, CI 1.5–61.4, P = .02) and iron deficiency anaemia (OR 4.8, CI 1.4–16.1, P = .01).

Conclusions

Influenza can be a severe illness, even in children without underlying medical conditions. The identification of Influenza B strain, history of food allergies and iron deficiency anaemia as predictors of severity in hospitalised cases warrants further investigation and may have important implications for preventative strategies to reduce the burden of childhood influenza.

Epidemiology of Australian Influenza-Related Paediatric Intensive Care Unit Admissions, 1997-2013

BACKGROUND

Influenza virus predictably causes an annual epidemic resulting in a considerable burden of illness in Australia. Children are disproportionately affected and can experience severe illness and complications, which occasionally result in death.

METHODS

We conducted a retrospective descriptive study using data collated in the Australian and New Zealand Paediatric Intensive Care (ANZPIC) Registry of influenza-related intensive care unit (ICU) admissions over a 17-year period (1997-2013, inclusive) in children <16 years old. National laboratory-confirmed influenza notifications were used for comparison.

RESULTS

Between 1997 and 2013, a total of 704 influenza-related ICU admissions were recorded, at a rate of 6.2 per 1,000 all-cause ICU admissions. Age at admission ranged from 0 days and 15.9 years (median = 2.1 years), with 135 (19.2%) aged <6 months. Pneumonia/pneumonitis and bronchiolitis were the most common primary diagnoses among influenza-related admissions (21.9% and 13.6%, respectively). More than half of total cases (59.2%) were previously healthy (no co-morbidities recorded), and in the remainder, chronic lung disease (16.7%) and asthma (12.5%) were the most common co-morbidities recorded. Pathogen co-detection occurred in 24.7% of cases, most commonly with respiratory syncytial virus or a staphylococcal species. Median length of all ICU admissions was 3.2 days (range 2.0 hours- 107.4 days) and 361 (51.3%) admissions required invasive respiratory support for a median duration of 4.3 days (range 0.2 hours- 107.5 days). There were 27 deaths recorded, 14 (51.9%) in children without a recorded co-morbidity.

CONCLUSION

Influenza causes a substantial number of ICU admissions in Australian children each year with the majority occurring in previously healthy children.

Should professionals caring for children be vaccinated? Community perspectives on health care and child care worker immunisation

OBJECTIVE

Several immunisations including influenza and pertussis are specifically recommended for healthcare workers (HCW) and childcare workers (CCW). This study aimed to assess community attitudes to HCW and CCW immunisation recommendations for pertussis and seasonal influenza.

METHODS

A cross-sectional study was conducted by Computer Assisted Telephone Interviewing (CATI) from April to May 2011. Statistical analyses used data weighted to the South Australian population by probability of selection, age, gender and geographical location using benchmarks derived from the 2009 Census population figures.

RESULTS

Almost all respondents supported vaccination of HCWs and CCWs against pertussis and influenza. For pertussis, 95.3% agreed nurses, 94.9% agreed doctors and 94.7% agreed CCWs have an obligation to be vaccinated. For influenza, 91.4% agreed nurses, 90.7% agreed doctors and 89.9% agreed CCWs have an obligation to be vaccinated. We identified higher support for protection against pertussis compared to influenza for all three groups of workers (p<0.001). There were higher concerns if CCWs compared to HCWs were not vaccinated against pertussis (OR=2.78) and influenza (OR=1.99). Young (18-30 years) and older age (60+ years) and lower educational attainment were predictors of support for HCWs and CCWs to be vaccinated against influenza. For pertussis, lower educational attainment was a predictor of support for HCWs immunisation.

CONCLUSIONS

Community support for CCW and HCW immunisation is strong with CCW immunisation was considered a priority. Pertussis immunisation was considered a higher priority than influenza immunisation for HCWs and CCWs. CCW immunisation should be considered for inclusion in public health immunisation programmes.

Influenza-related hospitalization and ED visits in children less than 5 years: 2000-2011

BACKGROUND AND OBJECTIVES

In the United States, recommendations for annual influenza vaccination gradually expanded from 2004 to 2008, to include all children aged ≥6 months. The effects of these policies on vaccine uptake and influenza-associated health care encounters are unclear. The objectives of the study were to examine the annual incidence of influenza-related health care encounters and vaccine uptake among children age 6 to 59 months from 2000-2001 through 2010-2011 in Davidson County, TN.

METHODS

We estimated the proportion of laboratory-confirmed influenza-related hospitalizations and emergency department (ED) visits by enrolling and testing children with acute respiratory illness or fever. We estimated influenza-related health care encounters by multiplying these proportions by the number of acute respiratory illness/fever hospitalizations and ED visits for county residents. We assessed temporal trends in vaccination coverage, and influenza-associated hospitalizations and ED visit rates.

RESULTS

The proportion of fully vaccinated children increased from 6% in 2000-2001 to 38% in 2010-2011 (P < .05). Influenza-related hospitalizations ranged from 1.9 to 16.0 per 10 000 children (median 4.5) per year. Influenza-related ED visits ranged from 89 to 620 per 10 000 children (median 143) per year. Significant decreases in hospitalizations (P < .05) and increases in ED visits (P < .05) over time were not clearly related to vaccination trends. Influenza-related encounters were greater when influenza A(H3N2) circulated than during other years with median rates of 8.2 vs 3.2 hospitalizations and 307 vs 143 ED visits per 10 000 children, respectively.

CONCLUSIONS

Influenza vaccination increased over time; however, the proportion of fully vaccinated children remained <50%. Influenza was associated with a substantial illness burden particularly when influenza A(H3N2) predominated.

Influenza H1N1pdm-specific maternal antibodies offer limited protection against wild-type virus replication and influence influenza vaccination in ferrets

OBJECTIVE

The objective was to study passively acquired influenza H1N1 pandemic (H1N1pdm) maternal antibody kinetics and its impact on subsequent influenza infection and vaccination in ferrets during an outbreak of the H1N1pdm.

DESIGN AND MAIN OUTCOME MEASURES

Infectivity of the H1N1pdm in the respiratory tract of ferrets was compared with the previous seasonal A/South Dakota/6/2007 (SD07, H1N1). Influenza-specific antibodies were quantitated and antibody-mediated protection against the homologous and heterologous H1N1 virus challenge infection was determined.

RESULTS

H1N1pdm virus was approximately 10 times more infectious than SD07 in ferrets, replicated to higher viral titers in the upper respiratory tract and shed for a longer duration. Influenza-specific antibodies after natural infection persisted much longer in the circulation than passively acquired maternal antibodies. The protection conferred by the maternal antibodies was limited to the homologous virus strain and was ineffective against SD07 and H3N2 virus. Serum antibodies from maternal transmission or passive transfer interfered with homologous vaccine strain-mediated antibody responses in the ferret. A booster immunization was required to elicit a high level of antibody.

CONCLUSIONS

The findings support the rationale for a prime and boost immunization strategy in young children in whom maternal antibodies are present.

Geographical heterogeneity and influenza infection within households

Background

Although it has been suggested that schoolchildren vaccination reduces influenza morbidity and mortality in the community, it is unknown whether geographical heterogeneity would affect vaccine effectiveness.

Methods

A 3-year prospective, non-randomized sero-epidemiological study was conducted during 2008–2011 by recruiting schoolchildren from both urban and rural areas. Respective totals of 124, 206, and 176 households were recruited and their household contacts were followed. Serum samples were collected pre-vaccination, one-month post-vaccination and post-season from children and household contacts for hemagglutination inhibition (HI) assay. A multivariate logistic model implemented with generalized estimation equations (GEE) was fitted with morbidity or a four-fold increase in HI titer of the household contacts for two consecutive sera as the dependent variable; with geographical location, vaccination status of each household and previous vaccination history as predictor variables.

Results

Although our results show no significant reduction in the proportion of infection or clinical morbidity among household contacts, a higher risk of infection, indicated by odds ratio > 1, was consistently observed among household children contacts from the un-vaccinated households after adjusting for confounding variables. Interestingly, a statistically significant lower risk of infection was observed among household adult contacts from rural area when compared to those from urban area (OR = 0.89; 95% CI: 0.82-0.97 for Year 2 and OR = 0.85; 95% CI: 0.75-0.96 for Year 3).

Conclusions

A significant difference in the risk of influenza infection among household adults due to geographical heterogeneity, independent of schoolchildren vaccination status, was revealed in this study. Its impact on vaccine effectiveness requires further study.

Influenza vaccination is not associated with detection of noninfluenza respiratory viruses in seasonal studies of influenza vaccine effectiveness

BACKGROUND

 The test-negative control study design is the basis for observational studies of influenza vaccine effectiveness (VE). Recent studies have suggested that influenza vaccination increases the risk of noninfluenza respiratory virus infection. Such an effect could create bias in VE studies using influenza-negative controls. We investigated the association between influenza infection, vaccination, and detection of other respiratory viruses among children <5 years old and adults ≥50 years old with acute respiratory illness who participated in seasonal studies of influenza vaccine effectiveness.

METHODS

 Nasal/nasopharyngeal samples collected from 2004–2005 through 2009–2010 were tested for 19 respiratory virus targets using a multiplex reverse-transcription polymerase chain reaction (RT-PCR) platform. Vaccination status was determined using a validated registry. Adjusted odds ratios for influenza and vaccination status were calculated using three different control groups: influenza-negative, other respiratory virus positive, and pan-negative.

RESULTS

 Influenza was detected in 12% of 2010 children and 20% of 1738 adults. Noninfluenza respiratory viruses were detected in 70% of children and 38% of adults without influenza. The proportion vaccinated did not vary between virus-positive controls and pan-negative controls in children (P = .62) or adults (P = .33). Influenza infection was associated with reduced odds of vaccination, but adjusted odds ratios differed by no more than 0.02 when the analysis used influenza-negative or virus-positive controls.

CONCLUSIONS

 Influenza vaccination was not associated with detection of noninfluenza respiratory viruses. Use of influenza-negative controls did not generate a biased estimate of vaccine effectiveness due to an effect of vaccination on other respiratory virus infections.

Mucosal immune responses predict clinical outcomes during influenza infection independently of age and viral load

RATIONALE

Children are an at-risk population for developing complications following influenza infection, but immunologic correlates of disease severity are not understood. We hypothesized that innate cellular immune responses at the site of infection would correlate with disease outcome.

OBJECTIVES

To test the immunologic basis of severe illness during natural influenza virus infection of children and adults at the site of infection.

METHODS

An observational cohort study with longitudinal sampling of peripheral and mucosal sites in 84 naturally influenza-infected individuals, including infants. Cellular responses, viral loads, and cytokines were quantified from nasal lavages and blood, and correlated to clinical severity.

MEASUREMENTS AND MAIN RESULTS

We show for the first time that although viral loads in children and adults were similar, innate responses in the airways were stronger in children and varied considerably between plasma and site of infection. Adjusting for age and viral load, an innate immune profile characterized by increased nasal lavage monocyte chemotactic protein-3, IFN-α2, and plasma IL-10 levels at enrollment predicted progression to severe disease. Increased plasma IL-10, monocyte chemotactic protein-3, and IL-6 levels predicted hospitalization. This inflammatory cytokine production correlated significantly with monocyte localization from the blood to the site of infection, with conventional monocytes positively correlating with inflammation. Increased frequencies of CD14(lo) monocytes were in the airways of participants with lower inflammatory cytokine levels.

CONCLUSIONS

An innate profile was identified that correlated with disease progression independent of viral dynamics and age. The airways and blood displayed dramatically different immune profiles emphasizing the importance of cellular migration and localized immune phenotypes.

Epidemiological aspects of influenza A related to climatic conditions during and after a pandemic period in the city of Salvador, Northeastern Brazil

During the influenza pandemic of 2009, the A(H1N1)pdm09, A/H3N2 seasonal and influenza B viruses were observed to be co-circulating with other respiratory viruses. To observe the epidemiological pattern of the influenza virus between May 2009-August 2011, 467 nasopharyngeal aspirates were collected from children less than five years of age in the city of Salvador. In addition, data on weather conditions were obtained. Indirect immunofluorescence, real-time transcription reverse polymerase chain reaction (RT-PCR), and sequencing assays were performed for influenza virus detection. Of all 467 samples, 34 (7%) specimens were positive for influenza A and of these, viral characterisation identified Flu A/H3N2 in 25/34 (74%) and A(H1N1)pdm09 in 9/34 (26%). Influenza B accounted for a small proportion (0.8%) and the other respiratory viruses for 27.2% (127/467). No deaths were registered and no pattern of seasonality or expected climatic conditions could be established. These observations are important for predicting the evolution of epidemics and in implementing future anti-pandemic measures.

Quality of life for parents of children with influenza-like illness: development and validation of Care-ILI-QoL

PURPOSE

Influenza-like illnesses (ILI) cause paediatric morbidity and affect the quality of life (QoL) of children and their parents. We have developed a disease-specific questionnaire (Care-ILI-QoL) to measure the QoL of caregivers of children with ILI.

METHODS

The drafting of the Care-ILI-QoL questionnaire was based on a systematic review, a quantitative survey, qualitative interviews with parents, and meetings with paediatricians. Children aged 6-48 months recruited from childcare centres in Sydney, Australia, were followed up during the 2011 influenza season. Care-ILI-QoL and SF-12v2 Acute Form were administered to the parent of a sick child 2 weeks after the onset of ILI, and again 2 weeks after the child had recovered. Exploratory factor analysis was conducted. Internal consistency, concurrent validity, discriminant validity, homogeneity of items, and responsiveness were tested.

RESULTS

Out of the 125 children enrolled from 48 childcare centres, 55 children had ILI (total 75 ILI episodes). Care-ILI-QoL was reduced from 25 to 16 items covering four factors: Daily Activities, Perceived Support, Social Life, and Emotions (Cronbach's alphas 0.90, 0.92, 0.78, and 0.72, respectively). Care-ILI-QoL has satisfactory concurrent and discriminant validity, good internal consistency, and excellent responsiveness. Total QoL and factor scores correlated well with SF-12v2 scores. Total QoL scores were significantly lower in parents who perceived their child as very/extremely sick, sacrificed 10 hours or more in work or recreation in caring for the child, or whose child had two or more general practitioner visits. Total QoL and factor scores were significantly higher after the child had recovered than when the child had ILI.

CONCLUSIONS

Care-ILI-QoL is the first ILI-specific QoL instrument for parents and is demonstrated to be valid and reliable in a developed country setting where the child is affected by ILI. It has the potential to be applied in clinical and research settings to assist measurement of disease burden, as a needs assessment tool for resources or to inform policy changes.

Economic burden of seasonal influenza B in France during winter 2010-2011

Background

In France, 2–15% of the population is affected annually by influenza, which causes significant socioeconomic disruption. Nevertheless, despite its importance for policy makers, few published studies have evaluated the impact of influenza B. Therefore, we assessed the costs associated with influenza B during 2010–2011 in France.

Methods

Cases of lab-confirmed influenza B were analyzed as part of the Influenza B in General Practice Study. Cost calculations were based on micro-costing methods according to the French Health Insurance (FHI) perspective (in Euros, 2011). Costs were compared between age groups using the Kruskal–Wallis test, and when significant, by multiple comparisons based on rank. Moreover, uncertainties were assessed using one-way sensitivity and probabilistic analyses. Overall economic burden was estimated by multiplying cost per patient, flu attack rate, and the French population.

Results

A total of 201 patients were included in the study. We found that the mean cost associated with Influenza B was 72€ (SD: 205) per patient: 70€ (SD: 262) for younger children, 50€ (SD: 195) for older children, 126€ (SD: 180) for adults, and 42€ (SD: 18) for elderly. Thus, we observed significantly different costs between the distinct age groups (p<0.0001). Finally, the economic burden of influenza B for the FHI was estimated to be 145 million Euros (95% CI: 88–201).

Conclusions

Our findings highlight the important impact of influenza B and encourage further investigation on policy regarding vaccination strategies in France.

Estimates and determinants of economic impacts from influenza-like illnesses caused by respiratory viruses in Australian children attending childcare: a cohort study

BACKGROUND

Influenza and other respiratory infections cause excess winter morbidity in children. This study assessed the economic impact of influenza-like illness (ILI) on families with children attending childcare using a societal perspective.

METHODS

We conducted a prospective cohort study in 90 childcare centres and one general practitioner clinics in Sydney, Australia, during 2010. Healthy children aged ≥6 months to <3 years were enrolled. Economic impacts of ILI (temperature ≥37·8°C or parental report of fever, plus ≥1 respiratory symptoms) were collected at 2 and 4 weeks after ILI onset by telephone interview. Parent-collected respiratory specimens were tested for respiratory viruses using real-time PCR (RT-PCR). Costs associated with healthcare visits, medication usage, carer time lost (work or recreation) and home care and/or additional childcare were collected. Influenza-like illness costs were described and further analysed using a Tobit model. Zero-inflated Poisson regression was employed to compare the numbers of healthcare visits for each ILI.

RESULTS

Of 381 children enrolled and analysed, 105 developed 124 ILIs. Specimens were available for 117 ILIs: five were positive by RT-PCR for A(H1N1)pdm09, 39 for adenovirus, 39 for rhinovirus, 15 for a coronavirus and 27 for a polyomavirus. The mean cost of all ILIs was AU$626 (95% confidence interval: AU$484-768) per ILI with no significant differences observed between viruses. Carers lost on average 13 hours of work and 3 hours of leisure time per ILI. Independent drivers of ILI costs were having both parents in employed work and longer duration of ILI. In multivariate analyses, four variables were significantly associated with an increased number of healthcare visits per ILI: non-Caucasian child, living in a detached house, both parents in employed work and having an ILI with one or more viruses identified.

CONCLUSIONS

For families with a child attending childcare, ILIs cause a substantial economic burden. An ILI in a child with working parents and/or with longer duration appears to cost more in monetary terms. Healthcare visits were increased if the child was non-Caucasian, lived in a detached house, had working parents or had a virus-positive ILI. Our findings on the estimates and determinants of economic impacts from respiratory virus infection highlight the importance and feasibility of an interdisciplinary (epidemiology/health economics) approach to such research.

Influenza infection in infants aged <6 months during the H1N1-09 pandemic: a hospital-based case series

AIMS

To document risk factors, clinical features and outcomes in infants <6 months old admitted with laboratory-confirmed influenza to The Children's Hospital at Westmead during the H1N1-09 pandemic.

METHODS

Prospective, hospital-based case series of infants admitted June-September 2009, identified by the Paediatric Active Enhanced Disease Surveillance system and supplemented by telephone interview post-discharge.

RESULTS

Thirty-two infants <6 months old had influenza A: 18 H1N1-09, 11 H3N2 and three unknown subtypes. After discharge, 28 (88%) families were telephoned and provided additional information. Documented risk factors included close contact with young children (46%), living with a smoker (36%), intensive or special care at birth (25%), pre-existing illness (16%) and preterm birth (14%). The number of persons per household was double the state average. Only 14% of mothers were vaccinated against seasonal influenza. Infants commonly presented with cough (69%), coryza (69%), lethargy (38%), fever (31%), dyspnoea (31%) and vomiting (28%). Complications included pneumonia (22%), and bacterial (9%) and viral (6%) co-infection. Five infants (15%) required admission to intensive care, and one was mechanically ventilated. Sixteen (57%) had ongoing respiratory problems, and six (21%) presented to the Emergency Department within 6 months of discharge.

CONCLUSIONS

These novel data are clinically important. Rates of influenza in infants may be reduced by vaccinating close contacts and minimising exposure to infected contacts and cigarette smoke.

Impact of children's influenza-like illnesses on parental quality of life: a qualitative study

AIMS

Influenza and influenza-like illness (ILI) in otherwise healthy children has considerable impact on their parents. This study explored the impact of children's ILI on parental quality of life (QoL).

METHODS

We conducted qualitative in-depth interviews with parents of children aged 6 months-3 years with severe ILI. Children from childcare centres in Sydney, Australia were followed through the 2010 influenza season. Questions covered child's symptoms, parents' experiences including medical care visits, impact on the family's daily routine, and emotional, physical and social well-being. Interviews were analysed using a modified grounded theory approach.

RESULTS

We conducted 21 interviews with 23 parents. Five main themes emerged: 'sudden changes in daily life', 'emotional impact', 'social isolation and relationship changes', 'importance of family and friend support' and 'interaction with the medical system'. Perceived practical and emotional support from family and/or friends and consultations with the doctor appeared to moderate the impact.

CONCLUSIONS

Severe ILI in children has a considerable impact on their parents' QoL, through disruptions of normal life routine, social isolation and stress in coping with the sick child. These impacts should be considered when introducing flexible workplace policies designed to minimise the impact on parental QoL. Prevention strategies such as vaccinating children against influenza may help alleviate this impact at a population level.

Prevention of influenza in healthy children

Healthy children are high transmitters of influenza and can experience poor influenza outcomes. Many questions remain about the efficacy and impect of preventive measures because most existing studies report imprecise proxies of influenza incidence, do not follow subjects throughout the entire influenza season and across multiple influenza seasons, or do not control for important factors such as timing of implementation and social contact patterns. Modeling and simulation are key methodologies to answer questions regarding influenza prevention. While vaccination may be the most efficacious existing intervention, variations in circulating strains and children's immune systems keep current vaccines from being fully protective, necessitating further clinical and economic studies and technology improvements. Hand hygiene appears to be an important adjunct but improving compliance, standardizing regimens and quantifying its impact remain challenging. Future studies should help better define the specific indications and circumstances for antiviral use and the role of nutritional supplements and nonpharmaceutical interventions.

Safety and tolerability of a 2009 trivalent inactivated split-virion influenza vaccine in infants, children and adolescents

OBJECTIVE

To evaluate the safety of CSL's split-virion inactivated trivalent 2009 Southern Hemisphere formulation influenza vaccine (TIV) in children.

METHODS

We enrolled 1992 healthy children into three groups: Cohorts A, ≥ 6 months to <3 years; B, ≥ 3 years to <9 years; and C, ≥ 9 years to <18 years. Children received one or two doses of 0.25 ml (22.5 μg haemagglutinin) or 0.5 ml (45 μg) TIV, depending on age and prior vaccination history. We collected post-vaccination solicited adverse event (AE) data (days 0-6), including fever (temperature: ≥ 37.5°C axilla, ≥ 38.0°C oral), unsolicited AEs (days 0-29) and serious AEs (SAEs) and new-onset chronic illnesses (NOCIs; to day 180 after last vaccination).

RESULTS

At least one solicited AE was reported by 80%/78%/78% of children in Cohorts A, B and C, respectively. Systemic AEs were more common among Cohort A (72% of participants), and local AEs were more common among Cohort C (71% of participants). Fever was more common in younger cohorts, in influenza vaccine-naïve children (29% of Cohort A receiving their first dose), and following first compared with second doses. Severe fever following a first dose prevented 20 participants receiving their second scheduled vaccine dose. A 7-month-old participant had a single uncomplicated febrile convulsion on the day of vaccination.

CONCLUSIONS

Nearly 80% of subjects reported at least one solicited AE following immunization. Fever prevalence was highest in vaccine-naïve Cohort A participants, similar to other paediatric studies using CSL vaccine. Further research to understand fever-related AEs in children following CSL's TIV is recommended.

A nice day for an infection? Weather conditions and social contact patterns relevant to influenza transmission

Although there is no doubt that significant morbidity and mortality occur during annual influenza epidemics, the role of contextual circumstances, which catalyze seasonal influenza transmission, remains unclear. Weather conditions are believed to affect virus survival, efficiency of transmission and host immunity, but seasonality may also be driven by a tendency of people to congregate indoors during periods of bad weather. To test this hypothesis, we combined data from a social contact survey in Belgium with local weather data. In the absence of a previous in-depth weather impact analysis of social contact patterns, we explored the possibilities and identified pitfalls. We found general dominance of day-type (weekend, holiday, working day) over weather conditions, but nonetheless observed an increase in long duration contacts ([Formula: see text]1 hour) on regular workdays with low temperatures, almost no precipitation and low absolute humidity of the air. Interestingly, these conditions are often assumed to be beneficial for virus survival and transmission. Further research is needed to establish the impact of the weather on social contacts. We recommend that future studies sample over a broad spectrum of weather conditions and day types and include a sufficiently large proportion of holiday periods and weekends.

Comparing the use of, and considering the need for, lumbar puncture in children with influenza or other respiratory virus infections

BACKGROUND

The clinical presentation of influenza in infancy may be similar to serious bacterial infection and be investigated with invasive procedures like lumbar puncture (LP), despite very limited evidence that influenza occurs concomitantly with bacterial meningitis, perhaps because the diagnosis of influenza is very often not established when the decision to perform LP is being considered.

METHODS

A retrospective medical record review was undertaken in all children presenting to the Children's Hospital at Westmead, Sydney, Australia, in one winter season with laboratory-confirmed influenza or other respiratory virus infections (ORVIs) but excluding respiratory syncytial virus, to compare the use of, and reflect on the need for, the performance of invasive diagnostic procedures, principally LP, but also blood culture, in influenza and non-influenza cases. We also determined the rate of concomitant bacterial meningitis or bacteraemia.

FINDINGS

Of 294 children, 51% had laboratory-confirmed influenza and 49% had ORVIs such as parainfluenza viruses (34%) and adenoviruses (15%). Of those with influenza, 18% had a LP and 71% had a blood culture performed compared with 6·3% and 55·5% in the ORVI group (for both P<0·01). In multivariate analysis, diagnosis of influenza was a strong independent predictor of both LP (P=0·02) and blood culture (P=0·05) being performed, and, in comparison with ORVIs, influenza cases were almost three times more likely to have a LP performed on presentation to hospital. One child with influenza (0·9%) had bacteraemia and none had meningitis.

INTERPRETATION

Children with influenza were more likely to undergo LP on presentation to hospital compared with those presenting with ORVIs. If influenza is confirmed on admission by near-patient testing, clinicians may be reassured and less inclined to perform LP, although if meningitis is clinically suspected, the clinician should act accordingly. We found that the risk of bacterial meningitis and bacteraemia was very low in hospitalised children with influenza and ORVIs. A systematic review should be performed to investigate this across a large number of settings.

Increased Prevalence of H1N1-Induced Severe Lower Respiratory Tract Diseases in Children With Atopic Sensitization

Purpose

Viral infection is the most common aggravating factor for childhood asthma. Asthma may be a risk factor for severe respiratory symptoms in children with lower respiratory tract infections of viral etiology. Influenza A infection enhances Th2-polarization to house dust mites during the acute phase and leads to lung dysfunction in a mouse model. However, there are no data on the relationship between atopic sensitization and H1N1 (Influenza A) infection in humans. To investigate whether atopic sensitization is associated with the severity of H1N1 pneumonia, we compared clinical features and the atopic sensitization rate between children with and without H1N1 infection.

Methods

Using reverse transcription-polymerase chain reactions, we investigated H1N1 virus infection in 214 children who were hospitalized with high fever and respiratory symptoms from September 2009 to February 2010. We also performed immunoassays for total and specific IgEs to six common aeroallergens. Atopy was defined as positivity for more than one specific IgE. The clinical severity of pneumonia was evaluated based on intensive care unit admission, oxygen therapy, steroid therapy, and atelectasis.

Results

There were 70 H1N1-positive children, 42.9% of whom had pneumonia. Children with H1N1 infection were older and had a higher prevalence of atopic sensitization and pneumonia compared with H1N1-negative children. The rate of atelectasis was higher in children with H1N1 pneumonia than in children with non-H1N1 pneumonia. Among children with H1N1 viral infection, those with atopic sensitization had a higher prevalence of intensive care unit admission and oxygen therapy, and a longer duration of hospitalization than non-atopic children. There were no differences between atopic and non-atopic children without H1N1 viral infection.

Conclusions

The prevalence of H1N1-induced severe lower respiratory tract diseases is higher in children with atopic sensitization.

Benefits to mother and child of influenza vaccination during pregnancy

Influenza virus infection contributes to substantial morbidity and mortality globally. Included in the list of groups at higher risk of either influenza infection or severe complications following influenza infection are pregnant women and their newborns. Influenza vaccination offers a safe and effective means to prevent or lessen the severity of influenza infections. Recent research has helped elucidate the impact of influenza infection and vaccination on pregnant women and their newborn children and young infants. This review summarizes recent findings in this area and identifies additional gaps in the evidence base that need to be addressed to appropriately inform vaccination policies worldwide, to protect pregnant women and their children from influenza and related complications.

A retrospective cross-sectional study of risk factors and clinical spectrum of children admitted to hospital with pandemic H1N1 influenza as compared to influenza A

OBJECTIVE

To compare risk factors for severe disease as measured by admission to hospital and intensive care unit (ICU) and other clinical outcomes in children with pandemic H1N1 (pH1N1) versus those with seasonal influenza.

DESIGN

Retrospective analysis of children admitted to hospital with pH1N1 versus seasonal influenza A.

SETTING

Canadian tertiary referral children's hospital.

PARTICIPANTS

All laboratory-identified cases of pH1N1 in children younger than 18 years admitted to hospital in 2009 (n=176) and all seasonal influenza A cases admitted to hospital from influenza seasons 2004-2005 to 2008-2009 (n=200). Children with onset of symptoms more than 3 days after admission were excluded.

PRIMARY AND SECONDARY OUTCOME MEASURES

Primary outcomes include admission to hospital and ICU and need for mechanical ventilation. Secondary outcomes include length of stay in hospital and duration of supplemental oxygen requirement.

RESULTS

Children admitted with pH1N1 were older than seasonal influenza A admissions (hospital admission: 6.5 vs 3.3 years, p<0.01; ICU admission: 7.3 vs 3.6 years, p=0.02). Children hospitalised with pH1N1 were more likely to have a pre-existing diagnosis of asthma (15% vs 5%, p<0.01); however, there was no difference in the severity of pre-existing asthma between the two groups. After controlling for obesity, asthma (OR 4.59, 95% CI 1.42 to 14.81) and age ≥5 years (OR 2.87, 95% CI 1.60 to 5.16) were more common risk factors in admitted children with pH1N1. Asthma was a significant predictor of the need for intensive care in patients with pH1N1 (OR 4.56, 95% CI 1.16 to 17.89) but not in patients with seasonal influenza A.

CONCLUSION

While most pH1N1 cases presented with classic influenza-like symptoms, risk factors for severe pH1N1 disease differed from seasonal influenza A. Older age and asthma were associated with increased admission to hospital and ICU for children with pH1N1.

Global burden of respiratory infections due to seasonal influenza in young children: a systematic review and meta-analysis

BACKGROUND

The global burden of disease attributable to seasonal influenza virus in children is unknown. We aimed to estimate the global incidence of and mortality from lower respiratory infections associated with influenza in children younger than 5 years.

METHODS

We estimated the incidence of influenza episodes, influenza-associated acute lower respiratory infections (ALRI), and influenza-associated severe ALRI in children younger than 5 years, stratified by age, with data from a systematic review of studies published between Jan 1, 1995, and Oct 31, 2010, and 16 unpublished population-based studies. We applied these incidence estimates to global population estimates for 2008 to calculate estimates for that year. We estimated possible bounds for influenza-associated ALRI mortality by combining incidence estimates with case fatality ratios from hospital-based reports and identifying studies with population-based data for influenza seasonality and monthly ALRI mortality.

FINDINGS

We identified 43 suitable studies, with data for around 8 million children. We estimated that, in 2008, 90 million (95% CI 49-162 million) new cases of influenza (data from nine studies), 20 million (13-32 million) cases of influenza-associated ALRI (13% of all cases of paediatric ALRI; data from six studies), and 1 million (1-2 million) cases of influenza-associated severe ALRI (7% of cases of all severe paediatric ALRI; data from 39 studies) occurred worldwide in children younger than 5 years. We estimated there were 28,000-111,500 deaths in children younger than 5 years attributable to influenza-associated ALRI in 2008, with 99% of these deaths occurring in developing countries. Incidence and mortality varied substantially from year to year in any one setting.

INTERPRETATION

Influenza is a common pathogen identified in children with ALRI and results in a substantial burden on health services worldwide. Sufficient data to precisely estimate the role of influenza in childhood mortality from ALRI are not available.

FUNDING

WHO; Bill & Melinda Gates Foundation.

The immunogenicity of a novel A (H1N1) vaccine in HIV-infected children

BACKGROUND

In October 2009, the United Kingdom Department of Health recommended vaccination of high-risk groups, including children with HIV, with a novel, oil-in-water AS03(B) adjuvanted Influenza A (H1N1) vaccine (Pandemrix). There were no published data available regarding the immunogenicity of this vaccine in such children.

OBJECTIVES

This study evaluated the immunogenicity of the adjuvanted Influenza A (H1N1) vaccine in HIV-infected children immunised according to national recommendations and assessed the impact of vaccination on individual CD4 counts and HIV viral loads.

METHODS

HIV-infected children attending outpatient appointments between 01 November and 31 December 2009 were offered two doses of H1N1 vaccine three weeks apart and a blood test before and 3 weeks after the second dose of vaccine. Serum antibody responses were determined by a haemagglutination inhibition (HAI) assay using standard methods.

RESULTS

Of the 39 children recruited for vaccination, 31 (median age 11.2, range 3.0-17.9 years) received both doses of vaccine and provided pre- and post-vaccination blood samples. Eight children (26%) had baseline HAI titres ≥ 1:32. After vaccination, 29 children (94%, 95% CI, 78.6-99.2%) had HAI titres ≥ 1:32 (seroprotection), of whom 27 (87.1%, 95% CI, 70.1-96.4%) had also had a four-fold rise in titres (seroconversion). In the univariate analysis, post-vaccination geometric mean titres (GMTs) were higher among the 21 children receiving highly active anti-retroviral therapy compared with the 10 treatment-naïve children (GMT 406 [95% CI 218-757] vs. 128 [49-336]; P=0.035), but this was no longer statistically significant when adjusted for prevaccine GMTs. There was no significant impact of vaccination on CD4+ T cell count or HIV viral load.

CONCLUSION

The AS03(B)-adjuvanted pandemic Influenza A (H1N1) vaccine is highly immunogenic and appears to be safe in HIV-infected children.

Community-acquired respiratory infections in young children with congenital heart diseases in the palivizumab era: the Spanish 4-season civic epidemiologic study

INTRODUCTION

To investigate the epidemiology of acute respiratory tract infections (ARIs) in children younger than 24 months old with hemodynamically significant congenital heart diseases. Primary aim: incidence of hospital admission due to ARI. Secondary aims: risk factors, etiologic agents, clinical outcomes, and usefulness of preventive measures.

PATIENTS AND METHODS

Prospective, multicenter, epidemiologic study conducted in 57 Spanish hospitals covering four 7-month seasons (2004-2008).

RESULTS

A total of 2613 patients were eligible for the study. Three hundred fifty-four patients (13.5%) (95% confidence interval: 12.3-14.9) required a total of 453 hospital admissions. Clinical diagnoses: bronchiolitis (54.1%), upper respiratory tract infection (21%), pneumonia (19.9%), and others (17.4%). Median length of hospital stay: 7.0 days. No etiologic agent was identified in two-thirds of the patients. In the remaining patients either a single agent (26.8%) or polymicrobial infection (5%) was identified. Respiratory syncytial virus (RSV) was the agent that was most commonly found (3.8% specific hospitalization rate). Children receiving adequate RSV prophylaxis (90.5%) had a 58.2% (95% confidence interval: 37.6-78.3) reduction in RSV hospitalization. Risk factors for admission included malnourishment, infant age, male gender, chromosome alterations, wheezing, inadequate RSV prophylaxis fulfillment, and siblings <11 years of age. Pediatric intensive care unit care was required in 21.8% of the admissions and 9 patients (0.34%) died.

CONCLUSIONS

Hospital admission rate and severity of ARI remain as important issues in hemodynamically significant congenital heart disease patients. The strict fulfillment of prophylactic recommendations against RSV is the only protective factor that can be modulated to decrease the ARI hospital admission rate.

Modeling the cost of influenza: the impact of missing costs of unreported complications and sick leave

Background

Estimating the economic impact of influenza is complicated because the disease may have non-specific symptoms, and many patients with influenza are registered with other diagnoses. Furthermore, in some countries like Norway, employees can be on paid sick leave for a specified number of days without a doctor's certificate ("self-reported sick leave") and these sick leaves are not registered. Both problems result in gaps in the existing literature: costs associated with influenza-related illness and self-reported sick leave are rarely included. The aim of this study was to improve estimates of total influenza-related health-care costs and productivity losses by estimating these missing costs.

Methods

Using Norwegian data, the weekly numbers of influenza-attributable hospital admissions and certified sick leaves registered with other diagnoses were estimated from influenza-like illness surveillance data using quasi-Poisson regression. The number of self-reported sick leaves was estimated using a Monte-Carlo simulation model of illness recovery curves based on the number of certified sick leaves. A probabilistic sensitivity analysis was conducted on the economic outcomes.

Results

During the 1998/99 through 2005/06 influenza seasons, the models estimated an annual average of 2700 excess influenza-associated hospitalizations in Norway, of which 16% were registered as influenza, 51% as pneumonia and 33% were registered with other diagnoses. The direct cost of seasonal influenza totaled US$22 million annually, including costs of pharmaceuticals and outpatient services. The annual average number of working days lost was predicted at 793 000, resulting in an estimated productivity loss of US$231 million. Self-reported sick leave accounted for approximately one-third of the total indirect cost. During a pandemic, the total cost could rise to over US$800 million.

Conclusions

Influenza places a considerable burden on patients and society with indirect costs greatly exceeding direct costs. The cost of influenza-attributable complications and the cost of self-reported sick leave represent a considerable part of the economic burden of influenza.

Risk factors and outcomes among children admitted to hospital with pandemic H1N1 influenza

BACKGROUND

Limited data are available on disease characteristics and outcomes of children with 2009 pandemic influenza A(H1N1) virus infection (pandemic H1N1 influenza) who have required hospital admission.

METHODS

We reviewed the charts of 58 children with pandemic H1N1 influenza admitted to a large pediatric hospital in Ontario, Canada, between May 8 and July 22, 2009. We compared risk factors, severity indicators and outcomes of these children with those of 200 children admitted with seasonal influenza A during the previous 5 years (2004/05 to 2008/09).

RESULTS

Children with pandemic H1N1 influenza were significantly older than those with seasonal influenza (median age 6.4 years v. 3.3 years). Forty-six (79%) of the children with pandemic H1N1 influenza had underlying medical conditions; of the other 12 who were previously healthy, 42% were under 2 years of age. Children admitted with pandemic H1N1 influenza were significantly more likely to have asthma than those with seasonal influenza (22% v. 6%). Two children had poorly controlled asthma, and 6 used inhaled medications only intermittently. The median length of stay in hospital was 4 days in both groups of children. Similar proportions of children required admission to the intensive care unit (21% of those with pandemic H1N1 influenza and 14% of those with seasonal influenza) and mechanical ventilation (12% and 10% respectively). None of the children admitted with pandemic H1N1 influenza died, as compared with 1 (0.4%) of those admitted with seasonal influenza.

INTERPRETATION

Pandemic H1N1 influenza did not appear to cause more severe disease than seasonal influenza A. Asthma appears to be a significant risk factor for severe disease, with no clear relation to severity of asthma. This finding should influence strategies for vaccination and pre-emptive antiviral therapy.