Pediatric influenza and illness severity: what is known and what questions remain?

Congenital Heart Defects and Concurrent Diagnoses in Influenza Hospitalization in the Pediatric Health Information System Study, 2004-2019

Influenza is associated with adverse outcomes in children, although modification by additional medical conditions is not well-documented. We aimed to compare outcomes in children with versus without congenital heart defects (CHDs) who were hospitalized for influenza. We retrospectively evaluated patients 1-18y hospitalized for influenza in the Pediatric Health Information (PHIS) database from 2004 to 2019. Outcomes were compared by CHD presence and then by CHD severity (minor biventricular, major biventricular, and single ventricle disease) using log-binomial regression adjusted for propensity scores accounting for age at admission, sex, and history of asthma. Outcomes included inpatient mortality, intensive care unit (ICU) admission, mechanical ventilation, and length of stay (LOS) > 12 days. To evaluate for effect modification by genetic diagnoses, analyses were repeated stratified by CHD and genetic diagnosis. Among 55,161 children hospitalized for influenza, 2369 (4.3%) had CHDs, including 963 with minor biventricular, 938 with major biventricular, and 468 with single ventricle CHDs. Adjusting for propensity scores, children with CHDs had higher mortality (4.1% versus 0.9%) compared to those without CHDs (risk ratio [RR] 2.5, 95% confidence interval [CI] 1.9-3.4). Children with CHDs were at higher risk of mechanical ventilation (RR 1.6, 95% CI 1.6-1.7), ICU admission (RR 1.9, 95% CI 1.8-2.1), and LOS > 12 days (RR 2.2, 95% CI 2.0-2.3). Compared to those with neither CHD nor genetic condition, children with both had significantly higher risk of all outcomes, with the largest difference for LOS > 12 days (RR 2.3, 95% CI 2.0-2.7). Children with CHDs hospitalized for influenza are particularly susceptible to adverse outcomes compared to those without CHDs. Future studies are needed to corroborate findings in light of influenza vaccination.

Influenza vaccination in children with pulmonary disease during the COVID-19 pandemic

INTRODUCTION

Influenza is associated with considerable respiratory morbidity and mortality. Healthcare authorities recommend immunization of all children as vaccinations protect vulnerable populations, minimize influenza triggered asthma attacks, and reduced the burden of respiratory illnesses during the SARS-CoV-2 pandemic. Medical professionals should counsel parents of children with chronic lung disease to receive annual influenza vaccinations as part of supportive care. We aimed to describe adherence to influenza vaccination in respiratory patients and identify potential reasons for non-vaccination.

METHODS

This study included questionnaires reviewing personal experience and beliefs regarding influenza vaccination, provided by parents of patients who visited the Pediatric Pulmonary Institute at Schneider Children's Medical Center with their children, during March-August 2021.

RESULTS

Of 198 parents who completed our questionnaire, 114 (57.3 %) vaccinated their children against influenza during that year. Average age was 6.9 ± 4.5 years. Demographic data were similar between the vaccinated and unvaccinated groups. Influenza vaccination rates differed significantly between parents who received an explanation from their primary physician and those who did not (65.4 % vs. 43.7 %, respectfully, p = 0.003), and parents who received explanations from a pulmonary specialist and those who did not (77.3 % vs. 48.8 %, respectively, p = 0.004). The combined recommendation of a primary physician and pulmonologist translated to a significantly higher vaccination rate among those who received such recommendations, as compared to those who did not (p < 0.001). Parents who believed in vaccine efficacy and safety were more likely to vaccinate their children (p < 0.001). Factors significantly affecting the decision of the parents to have their child vaccinated were their knowledge, beliefs, and conceptions about the vaccine.

CONCLUSIONS

Pediatric respiratory patients' influenza vaccination rate was 57 %. Major factors encouraging vaccination were correct parental knowledge and receiving recommendations from their primary physician\pulmonologist. This emphasizes the need for providing patients with information, by first explaining the vaccine's importance to physicians.

Severity of influenza-associated hospitalisations by influenza virus type and subtype in the USA, 2010-19: a repeated cross-sectional study

BACKGROUND

Influenza burden varies across seasons, partly due to differences in circulating influenza virus types or subtypes. Using data from the US population-based surveillance system, Influenza Hospitalization Surveillance Network (FluSurv-NET), we aimed to assess the severity of influenza-associated outcomes in individuals hospitalised with laboratory-confirmed influenza virus infections during the 2010-11 to 2018-19 influenza seasons.

METHODS

To evaluate the association between influenza virus type or subtype causing the infection (influenza A H3N2, A H1N1pdm09, and B viruses) and in-hospital severity outcomes (intensive care unit [ICU] admission, use of mechanical ventilation or extracorporeal membrane oxygenation [ECMO], and death), we used FluSurv-NET to capture data for laboratory-confirmed influenza-associated hospitalisations from the 2010-11 to 2018-19 influenza seasons for individuals of all ages living in select counties in 13 US states. All individuals had to have an influenza virus test within 14 days before or during their hospital stay and an admission date between Oct 1 and April 30 of an influenza season. Exclusion criteria were individuals who did not have a complete chart review; cases from sites that contributed data for three or fewer seasons; hospital-onset cases; cases with unidentified influenza type; cases of multiple influenza virus type or subtype co-infection; or individuals younger than 6 months and ineligible for the influenza vaccine. Logistic regression models adjusted for influenza season, influenza vaccination status, age, and FluSurv-NET site compared odds of in-hospital severity by virus type or subtype. When missing, influenza A subtypes were imputed using chained equations of known subtypes by season.

FINDINGS

Data for 122 941 individuals hospitalised with influenza were captured in FluSurv-NET from the 2010-11 to 2018-19 seasons; after exclusions were applied, 107 941 individuals remained and underwent influenza A virus imputation when missing A subtype (43·4%). After imputation, data for 104 969 remained and were included in the final analytic sample. Averaging across imputed datasets, 57·7% (weighted percentage) had influenza A H3N2, 24·6% had influenza A H1N1pdm09, and 17·7% had influenza B virus infections; 16·7% required ICU admission, 6·5% received mechanical ventilation or ECMO, and 3·0% died (95% CIs had a range of less than 0·1% and are not displayed). Individuals with A H1N1pdm09 had higher odds of in-hospital severe outcomes than those with A H3N2: adjusted odds ratios (ORs) for A H1N1pdm09 versus A H3N2 were 1·42 (95% CI 1·32-1·52) for ICU admission; 1·79 (1·60-2·00) for mechanical ventilation or ECMO use; and 1·25 (1·07-1·46) for death. The adjusted ORs for individuals infected with influenza B versus influenza A H3N2 were 1·06 (95% CI 1·01-1·12) for ICU admission, 1·14 (1·05-1·24) for mechanical ventilation or ECMO use, and 1·18 (1·07-1·31) for death.

INTERPRETATION

Despite a higher burden of hospitalisations with influenza A H3N2, we found an increased likelihood of in-hospital severe outcomes in individuals hospitalised with influenza A H1N1pdm09 or influenza B virus. Thus, it is important for individuals to receive an annual influenza vaccine and for health-care providers to provide early antiviral treatment for patients with suspected influenza who are at increased risk of severe outcomes, not only when there is high influenza A H3N2 virus circulation but also when influenza A H1N1pdm09 and influenza B viruses are circulating.

FUNDING

The US Centers for Disease Control and Prevention.

Clinical outcomes of COVID-19 and influenza in hospitalized children <5 years in the US

Introduction

We compared hospitalization outcomes of young children hospitalized with COVID-19 to those hospitalized with influenza in the United States.

Methods

Patients aged 0-<5 years hospitalized with an admission diagnosis of acute COVID-19 (April 2021-March 2022) or influenza (April 2019-March 2020) were selected from the PINC AI Healthcare Database Special Release. Hospitalization outcomes included length of stay (LOS), intensive care unit (ICU) admission, oxygen supplementation, and mechanical ventilation (MV). Inverse probability of treatment weighting was used to adjust for confounders in logistic regression analyses.

Results

Among children hospitalized with COVID-19 (n = 4,839; median age: 0 years), 21.3% had an ICU admission, 19.6% received oxygen supplementation, 7.9% received MV support, and 0.5% died. Among children hospitalized with influenza (n = 4,349; median age: 1 year), 17.4% were admitted to the ICU, 26.7% received oxygen supplementation, 7.6% received MV support, and 0.3% died. Compared to children hospitalized with influenza, those with COVID-19 were more likely to have an ICU admission (adjusted odds ratio [aOR]: 1.34; 95% confidence interval [CI]: 1.21-1.48). However, children with COVID-19 were less likely to receive oxygen supplementation (aOR: 0.71; 95% CI: 0.64-0.78), have a prolonged LOS (aOR: 0.81; 95% CI: 0.75-0.88), or a prolonged ICU stay (aOR: 0.56; 95% CI: 0.46-0.68). The likelihood of receiving MV was similar (aOR: 0.94; 95% CI: 0.81, 1.1).

Conclusions

Hospitalized children with either SARS-CoV-2 or influenza had severe complications including ICU admission and oxygen supplementation. Nearly 10% received MV support. Both SARS-CoV-2 and influenza have the potential to cause severe illness in young children.

Efficient symptomatic treatment and viral load reduction for children with influenza virus infection by nasal-spraying Bacillus spore probiotics

Influenza virus is a main cause of acute respiratory tract infections (ARTIs) in children. This is the first double-blind, randomized, and controlled clinical trial examining the efficacy of nasal-spraying probiotic LiveSpo Navax, which contains 5 billion of Bacillus subtilis and B. clausii spores in 5 mL, in supporting treatment of influenza viral infection in pediatric patients. We found that the nasal-spraying Bacillus spores significantly shortened the recovery period and overall treatment by 2 days and increased treatment effectiveness by 58% in resolving all ARTIs' symptoms. At day 2, the concentrations of influenza virus and co-infected bacteria were reduced by 417 and 1152 folds. Additionally, the levels of pro-inflammatory cytokines IL-8, TNF-α, and IL-6 in nasopharyngeal samples were reduced by 1.1, 3.7, and 53.9 folds, respectively. Compared to the standard control group, treatment regimen with LiveSpo Navax demonstrated significantly greater effectiveness, resulting in 26-fold reduction in viral load, 65-fold reduction in bacterial concentration, and 1.1-9.5-fold decrease in cytokine levels. Overall, nasal-spraying Bacillus spores can support the symptomatic treatment of influenza virus-induced ARTIs quickly, efficiently and could be used as a cost-effective supportive treatment for respiratory viral infection in general.Clinical trial registration no: NCT05378022 on 17/05/2022.

Early peripheral blood lymphocyte subsets and cytokines in predicting the severity of influenza B virus pneumonia in children

Background

Children with influenza B virus infection have a higher susceptibility and higher severity of illness. The activation and disorder of immune function play an important role in the severity of influenza virus infection. This study aims to investigate whether early lymphocyte count and cytokines can provide predictive value for the progression in children with influenza B virus pneumonia.

Methods

A retrospective cohort study was conducted to analyze the clinical data of children with influenza B virus pneumonia from December 1, 2021, to March 31, 2022, in the National Children's Regional Medical Center (Shengjing Hospital of China Medical University). According to the severity of the disease, the children were divided into a mild group and a severe group, and the clinical characteristics, routine laboratory examination, lymphocyte subsets, and cytokines were compared.

Results

A total of 93 children with influenza B virus pneumonia were enrolled, including 70 cases in the mild group and 23 cases in the severe group. Univariate analysis showed that drowsiness, dyspnea, white blood cell (WBC), lymphocytes, monocytes, procalcitonin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatine kinase-MB (CK-MB), lactate dehydrogenase (LDH), fibrinogen (FIB), Immunoglobulin M (IgM), lung consolidation, total T cell count, CD4⁺ T cell count, CD8⁺ T cell count, NK cell count, NK cell % and B cell % had statistical differences between the mild and severe groups (P<0.05). In multivariate logistic regression analysis, reduced ALT (OR = 1.016), FIB (OR = 0.233), CD8⁺ T cell count (OR = 0.993) and NK cell count (OR = 0.987) were independently associated with the development of severe influenza B virus pneumonia.

Conclusions

The levels of T lymphocytes and NK cells were related to the progression of influenza B virus pneumonia in children, and the reduction of CD8⁺ T cell count and NK cell count can be used as independent risk factors for predicting the severity of influenza B virus pneumonia.

Comparison of Influenza and Coronavirus Disease 2019-Associated Hospitalizations Among Children Younger Than 18 Years Old in the United States: FluSurv-NET (October-April 2017-2021) and COVID-NET (October 2020-September 2021)

BACKGROUND

Influenza virus and SARS-CoV-2 are significant causes of respiratory illness in children.

METHODS

Influenza- and COVID-19-associated hospitalizations among children <18 years old were analyzed from FluSurv-NET and COVID-NET, 2 population-based surveillance systems with similar catchment areas and methodology. The annual COVID-19-associated hospitalization rate per 100 000 during the ongoing COVID-19 pandemic (1 October 2020-30 September 2021) was compared with influenza-associated hospitalization rates during the 2017-2018 through 2019-2020 influenza seasons. In-hospital outcomes, including intensive care unit (ICU) admission and death, were compared.

RESULTS

Among children <18 years, the COVID-19-associated hospitalization rate (48.2) was higher than influenza-associated hospitalization rates: 2017-2018 (33.5), 2018-2019 (33.8), and 2019-2020 (41.7). The COVID-19-associated hospitalization rate was higher among adolescents 12-17 years old (COVID-19: 59.9; influenza range: 12.2-14.1), but similar or lower among children 5-11 (COVID-19: 25.0; influenza range: 24.3-31.7) and 0-4 (COVID-19: 66.8; influenza range: 70.9-91.5) years old. Among children <18 years, a higher proportion with COVID-19 required ICU admission compared with influenza (26.4% vs 21.6%; P < .01). Pediatric deaths were uncommon during both COVID-19- and influenza-associated hospitalizations (0.7% vs 0.5%; P = .28).

CONCLUSIONS

In the setting of extensive mitigation measures during the COVID-19 pandemic, the annual COVID-19-associated hospitalization rate during 2020-2021 was higher among adolescents and similar or lower among children <12 years compared with influenza during the 3 seasons before the COVID-19 pandemic. COVID-19 adds substantially to the existing burden of pediatric hospitalizations and severe outcomes caused by influenza and other respiratory viruses.

Prevalence of SARS-CoV-2 and Influenza Coinfection and Clinical Characteristics Among Children and Adolescents Aged <18 Years Who Were Hospitalized or Died with Influenza - United States, 2021-22 Influenza Season

The 2022-23 influenza season shows an early rise in pediatric influenza-associated hospitalizations (1). SARS-CoV-2 viruses also continue to circulate (2). The current influenza season is the first with substantial co-circulation of influenza viruses and SARS-CoV-2 (3). Although both seasonal influenza viruses and SARS-CoV-2 can contribute to substantial pediatric morbidity (3-5), whether coinfection increases disease severity compared with that associated with infection with one virus alone is unknown. This report describes characteristics and prevalence of laboratory-confirmed influenza virus and SARS-CoV-2 coinfections among patients aged <18 years who had been hospitalized or died with influenza as reported to three CDC surveillance platforms during the 2021-22 influenza season. Data from two Respiratory Virus Hospitalizations Surveillance Network (RESP-NET) platforms (October 1, 2021-April 30, 2022),§ and notifiable pediatric deaths associated¶ with influenza virus and SARS-CoV-2 coinfection (October 3, 2021-October 1, 2022)** were analyzed. SARS-CoV-2 coinfections occurred in 6% (32 of 575) of pediatric influenza-associated hospitalizations and in 16% (seven of 44) of pediatric influenza-associated deaths. Compared with patients without coinfection, a higher proportion of those hospitalized with coinfection received invasive mechanical ventilation (4% versus 13%; p = 0.03) and bilevel positive airway pressure or continuous positive airway pressure (BiPAP/CPAP) (6% versus 16%; p = 0.05). Among seven coinfected patients who died, none had completed influenza vaccination, and only one received influenza antivirals.†† To help prevent severe outcomes, clinicians should follow recommended respiratory virus testing algorithms to guide treatment decisions and consider early antiviral treatment initiation for pediatric patients with suspected or confirmed influenza, including those with SARS-CoV-2 coinfection who are hospitalized or at increased risk for severe illness. The public and parents should adopt prevention strategies including considering wearing well-fitted, high-quality masks when respiratory virus circulation is high and staying up-to-date with recommended influenza and COVID-19 vaccinations for persons aged ≥6 months.

Exploration of influenza incidence prediction model based on meteorological factors in Lanzhou, China, 2014-2017

Humans are susceptible to influenza. The influenza virus spreads quickly and behave seasonally. The seasonality and spread of influenza are often associated with meteorological factors and have spatio-temporal differences. Based on the influenza cases and daily average meteorological factors in Lanzhou from 2014 to 2017, this study firstly aimed to analyze the characteristics of influenza incidence in Lanzhou and the impact of meteorological factors on influenza activities. Then, SARIMA(X) models for the prediction were established. The influenza cases in Lanzhou from 2014 to 2017 was more male than female, and the younger the age, the higher the susceptibility; the epidemic characteristics showed that there is a peak in winter, a secondary peak in spring, and a trough in summer and autumn. The influenza cases in Lanzhou increased with increasing daily pressure, decreasing precipitation, average relative humidity, hours of sunshine, average daily temperature and average daily wind speed. Low temperature was a significant driving factor for the increase of transmission intensity of seasonal influenza. The SARIMAX (1,0,0)(1,0,1)[12] multivariable model with average temperature has better prediction performance than the university model. This model is helpful to establish an early warning system, and provide important evidence for the development of influenza control policies and public health interventions.

Pyroptosis and respiratory diseases: A review of current knowledge

Pyroptosis is a relatively newly discovered programmed cell death accompanied by an inflammatory response. In the classical view, pyroptosis is mediated by caspases-1,-4,-5,-11 and executed by GSDMD, however, recently it was demonstrated that caspase-3 and-8 also participate in the process of pyroptosis, by cleaving GSDMD/E and GSDMD respectively. Different from autophagy and apoptosis, many pores are formed on the cell membrane during pyroptosis, which makes the cell membrane lose its integrity, eventually leading to the release of cytokines interleukin(IL)-1β and IL-18. When the body is infected with pathogens or exposed to some stimulations, pyroptosis could play an immune defense role. It is found that pyroptosis exists widely in infectious and inflammatory respiratory diseases such as acute lung injury, bronchial dysplasia, chronic obstructive pulmonary disease, and asthma. Excessive pyroptosis may accompany airway inflammation, tissue injury, and airway damage, and induce an inflammatory reaction, leading to more serious damage and poor prognosis of respiratory diseases. This review summarizes the relationship between pyroptosis and related respiratory diseases.

Hospitalization of Children Aged <5 Years Due to Influenza: Study Based on the National Hospitalization Registry

Background: Influenza constitutes a significant health care burden that can be related to an increased morbidity and mortality. The aim of the study is to show up-to-date information on influenza hospitalization cases in Poland in children aged <5 years. Methods: The data used in the study were hospitalization records from 2015−2019, which had been gathered in a Nationwide General Hospital Morbidity Study and made available by the National Institute of Public Health. Results: 8565 records of patients with influenza were subject to analysis. The mean and median age of the patients were 2.2 and 2.1 years, respectively. Influenza hospitalization incidence was estimated at 90 per 100,000 person-years (PY) in children aged <5 years. The number of hospitalization cases was significantly higher in patients living in urban regions than in those living in rural regions (97 vs. 77 per 100,000 PY; p < 0.001). The age of patients living in urban regions was significantly lower than the age of patients living in rural regions (2.2 vs. 2.3 years; p < 0.001). A statistically significant increase in hospitalization was observed. Conclusions: The reported increasing trend in hospitalizations indicates the need to take focused measures. Presented data may be useful in comparative analyses in a European context.

Influenza clinical testing and oseltamivir treatment in hospitalized children with acute respiratory illness, 2015-2016

BACKGROUND

Antiviral treatment is recommended for all hospitalized children with suspected or confirmed influenza, regardless of their risk profile. Few data exist on adherence to these recommendations, so we sought to determine factors associated with influenza testing and antiviral treatment in children.

METHODS

Hospitalized children <18 years of age with acute respiratory illness (ARI) were enrolled through active surveillance at pediatric medical centers in seven cities between 11/1/2015 and 6/30/2016; clinical information was obtained from parent interview and chart review. We used generalized linear mixed-effects models to identify factors associated with influenza testing and antiviral treatment.

RESULTS

Of the 2299 hospitalized children with ARI enrolled during one influenza season, 51% (n = 1183) were tested clinically for influenza. Clinicians provided antiviral treatment for 61 of 117 (52%) patients with a positive influenza test versus 66 of 1066 (6%) with a negative or unknown test result. In multivariable analyses, factors associated with testing included neuromuscular disease (aOR = 5.35, 95% CI [3.58-8.01]), immunocompromised status (aOR = 2.88, 95% CI [1.66-5.01]), age (aOR = 0.93, 95% CI [0.91-0.96]), private only versus public only insurance (aOR = 0.78, 95% CI [0.63-0.98]), and chronic lung disease (aOR = 0.64, 95% CI [0.51-0.81]). Factors associated with antiviral treatment included neuromuscular disease (aOR = 1.86, 95% CI [1.04, 3.31]), immunocompromised state (aOR = 2.63, 95% CI [1.38, 4.99]), duration of illness (aOR = 0.92, 95% CI [0.84, 0.99]), and chronic lung disease (aOR = 0.60, 95% CI [0.38, 0.95]).

CONCLUSION

Approximately half of children hospitalized with influenza during the 2015-2016 influenza season were treated with antivirals. Because antiviral treatment for influenza is associated with better health outcomes, further studies of subsequent seasons would help evaluate current use of antivirals among children and better understand barriers for treatment.

Complications of influenza in 272 adult and pediatric patients in a German university hospital during the seasonal epidemic 2017-2018

Background

The influenza season 2017–2018 of the northern hemisphere was the highest since 2001 and was caused predominantly by influenza B virus.

Methods

We performed a retrospective analysis of all patients in a university hospital in northern Germany with laboratory-confirmed influenza during the winter season 2017–2018 and analyzed underlying conditions, complications, and outcome.

Results

A total of 272 cases of influenza were diagnosed: 70 influenza A (25.7%), 201 influenza B (73.9%), and 1 co-infection. Of 182 adults, 145 were hospitalized, 73 developed pneumonia, 11 developed myocardial infarction, two a transient ischemic attack, one a stroke, and one perimyocarditis. Eleven of the 145 hospitalized adult patients (7.6%) died, ten of them because of pneumonia. All of them had preexisting diseases. Pneumonia was associated with a mortality of 13.7%. Underlying cardiac insufficiency was correlated with higher mortality (7/51 with versus 4/126 patients without cardiac insufficiency; p < 0.05). Ninety cases of influenza were diagnosed in 89 children (30 A, 60 B), one child had first influenza B, then influenza A. Twenty-eight children (31%) were hospitalized, 15 children developed one or more complications (lower respiratory tract infections, meningeal irritations, febrile seizures, otitis media, myositis). No child died. Influenza vaccination status was known in 149 adult patients, pneumonia occurred more frequently in non-vaccinated individuals (43/90; 47.8%) than in vaccinated patients (18/59; 30.5%, p < 0.05).

Conclusion

Patients with influenza should be monitored for secondary pneumonia and myocardial infarction, and vaccination should be enforced especially in patients with coronary heart disease and cardiac insufficiency.

A Biological Insight into the Susceptibility to Influenza Infection in Junior Rats by Comprehensive Analysis of lncRNA Profiles

Long noncoding RNAs (lncRNAs) have been reported to participate in regulating many biological processes, including immune response to influenza A virus (IAV). However, the association between lncRNA expression profiles and influenza infection susceptibility has not been well elucidated. Here, we analyzed the expression profiles of lncRNAs, miRNAs, and mRNAs among IAV-infected adult rat (IAR), normal adult rat (AR), IAV-infected junior rat (IJR), and normal junior rat (JR) by RNA sequencing. Compared with differently expressed lncRNAs (DElncRNAs) between AR and IAR, 24 specific DElncRNAs were found between IJR and JR. Then, based on the fold changes and P value, the top 5 DElncRNAs, including 3 upregulated and 2 downregulated lncRNAs, were chosen to establish a ceRNA network for further disclosing their regulatory mechanisms. To visualize the differentially expressed genes in the ceRNA network, GO and KEGG pathway analysis was performed to further explore their roles in influenza infection of junior rats. The results showed that the downregulated DElncRNA-target genes were mostly enriched in the IL-17 signaling pathway. It indicated that the downregulated lncRNAs conferred the susceptibility of junior rats to IAV via mediating the IL-17 signaling pathway.

Inactivated influenza vaccine effectiveness among department of defense beneficiaries aged 6 months-17 years, 2016-2017 through 2019-2020 influenza seasons

A test-negative case-control study was conducted to assess inactivated influenza vaccine effectiveness (VE) in children aged 6 months-17 years. The database was developed from the US Department of Defense Global Respiratory Pathogen Surveillance Program over four consecutive influenza seasons from 2016 to 2020. A total of 9,385 children including 4,063 medically attended, laboratory-confirmed influenza-positive cases were identified for VE analysis. A generalized linear mixed model with logit link and binomial distribution was used to estimate the VE. The adjusted VE for children was 42% [95% confidence interval (CI): 37-47%] overall, including 55% (95% CI: 47-61%) for influenza A(H1N1)pdm09, 37% (95% CI: 28-45%) for influenza A(H3N2), and 49% (95% CI: 41-55%) for influenza B. The analysis by age groups indicated that the adjusted VE in children aged 6 months-4 years was higher against influenza A(H1N1)pdm09 and influenza B, and comparable against influenza A(H3N2), compared to those in children aged 5-17 years. Further age-stratified analysis showed that the VE against any types of influenza was low and non-significant for children aged 6-11 months (33%; 95% CI:-2-56%), but it was high (54%; 95% CI: 34-67%) in children aged 12-23 months, and then declined linearly with increasing age. In conclusion, the inactivated influenza vaccination was moderately effective against influenza infection, based on the analysis from a large number of children aged 6 months-17 years over multiple influenza seasons.

General Characteristics of Children with Single- and Co-Infections and Febrile Seizures with a Main Focus on Respiratory Pathogens: Preliminary Results

Febrile seizures (FS) affect up to 5% of children. The pathogen etiology in regard of viral loads has never been investigated. In a prospective cohort study we investigated the correlation between virus type and quantity in nasopharyngeal aspirates (NPAs) and the clinical characteristics in pediatric patients with a FS. From January 2014 to April 2016, 184 children with a FS were prospectively enrolled. The mean age of all included children was 26.7 ± 18.3 months with a male to female ratio of 1.4:1. Males with an acute disease and a short duration or absence of prior symptoms had a higher risk for complex FS. The majority of patients with FS presented with a generalized convulsion (180; 98%) and was admitted to hospital (178; 97%). Overall, 79 (43%) single and in 59 (32%) co-infections were detected. Human herpes virus 6 (HHV6), influenza, adenovirus (AV) and rhinovirus (RV) were the dominant pathogens, all detected with clinically significant high viral loads. HHV6 positive cases were significantly younger and less likely to have a positive family/personal history for FS. Influenza positives showed a higher rate of complex seizures, lower leukocyte and higher monocyte counts. AV positive cases were more likely to have a positive family history for FS and showed higher C-reactive protein values. In conclusion, a high viral load may contribute to the development of a FS in respiratory tract infections.

Behavior of hospitalized severe influenza cases according to the outcome variable in Catalonia, Spain, during the 2017-2018 season

Influenza is an important cause of severe illness and death among patients with underlying medical conditions and in the elderly. The aim of this study was to investigate factors associated with ICU admission and death in patients hospitalized with severe laboratory-confirmed influenza during the 2017–2018 season in Catalonia. An observational epidemiological case-to-case study was carried out. Reported cases of severe laboratory-confirmed influenza requiring hospitalization in 2017–2018 influenza season were included. Mixed-effects regression analysis was used to estimate the factors associated with ICU admission and death. A total of 1306 cases of hospitalized severe influenza cases were included, of whom 175 (13.4%) died and 217 (16.6%) were ICU admitted. Age 65–74 years and ≥ 75 years and having ≥ 2 comorbidities were positively associated with death (aOR 3.19; 95%CI 1.19–8.50, aOR 6.95, 95%CI 2.76–1.80 and aOR 1.99; 95%CI 1.12–3.52, respectively). Neuraminidase inhibitor treatment and pneumonia were negatively associated with death. The 65–74 years and ≥ 75 years age groups were negatively associated with ICU admission (aOR 0.41; 95%CI 0.23–0.74 and aOR 0.30; 95%CI 0.17–0.53, respectively). A factor positively associated with ICU admission was neuraminidase inhibitor treatment. Our results support the need to investigate the worst outcomes of hospitalized severe cases, distinguishing between death and ICU admission.

Reduced Influenza B-Specific Postvaccination Antibody Cross-reactivity in the B/Victoria Lineage-Predominant 2019/20 Season

BACKGROUND

The influenza activity of the 2019/20 season remained high and widespread in the United States with type B viruses predominating the early season. The majority of B viruses characterized belonged to B/Victoria (B/Vic) lineage and contained a triple deletion of amino acid (aa) 162-164 in hemagglutinin (3DEL). These 3DEL viruses are antigenically distinct from B/Colorado/06/2017 (CO/06)-the B/Vic vaccine component of the 2018/19 and 2019/20 seasons representing the viruses with a double deletion of aa 162-163 in hemagglutinin (2DEL).

METHODS

We performed molecular characterization and phylogenetic analysis of circulating B/Vic viruses. We also conducted hemagglutination inhibition (HAI) assay using archived human postvaccination sera collected from healthy subjects administered with different types of 2018/19 or 2019/20 seasonal vaccines. Their HAI cross-reactivity to representative 3DEL viruses was analyzed.

RESULTS

The CO/06-specific human postvaccination sera, after being adjusted for vaccine type, had significantly reduced HAI cross-reactivity toward representative 3DEL viruses, especially the 136E+150K subgroup. The geometric mean titers against 3DEL viruses containing 136E+150K mutations were 1.6-fold lower in all populations (P = .051) and 1.9-fold lower in adults (P = .016) compared with those against the 136E+150N viruses.

CONCLUSIONS

Our results indicate that postvaccination antibodies induced by the B/Vic vaccine component of the 2019/20 influenza season had reduced HAI cross-reactivity toward predominant 3DEL viruses in the United States. A close monitoring of the 3DEL 136E+150K subgroup is warranted should this subgroup return and predominate the 2020/21 influenza season.

Natural mucosal barriers and COVID-19 in children

BACKGROUND

Coronavirus disease 2019 (COVID-19) is more benign in children compared with adults for unknown reasons. This contrasts with other respiratory viruses where disease manifestations are often more severe in children. We hypothesize that a more robust early innate immune response to SARS coronavirus 2 (SARS-CoV-2) protects against severe disease.

METHODS

Clinical outcomes, SARS-CoV-2 viral copies, and cellular gene expression were compared in nasopharyngeal swabs obtained at the time of presentation to the emergency department from 12 children and 27 adults using bulk RNA sequencing and quantitative reverse-transcription PCR. Total protein, cytokines, and anti–SARS-CoV-2 IgG and IgA were quantified in nasal fluid.

RESULTS

SARS-CoV-2 copies, angiotensin-converting enzyme 2, and TMPRSS2 gene expression were similar in children and adults, but children displayed higher expression of genes associated with IFN signaling, NLRP3 inflammasome, and other innate pathways. Higher levels of IFN-α2, IFN-γ, IP-10, IL-8, and IL-1β protein were detected in nasal fluid in children versus adults. Children also expressed higher levels of genes associated with immune cells, whereas expression of those associated with epithelial cells did not differ in children versus adults. Anti–SARS-CoV-2 IgA and IgG were detected at similar levels in nasal fluid from both groups. None of the children required supplemental oxygen, whereas 7 adults did (P = 0.03); 4 adults died.

CONCLUSION

These findings provide direct evidence of a more vigorous early mucosal immune response in children compared with adults and suggest that this contributes to favorable clinical outcomes.

FUNDING

NIH grants R01 AI134367, UL1 TR002556, T32 AI007501, T32GM007288, P30 AI124414; an Albert Einstein College of Medicine Dean’s COVID-19 Pilot Research Award; and the Eric J. Heyer, MD, PhD Translational Research Pilot Project Award.

Natural Mucosal Barriers and COVID-19 in Children

COVID-19 is more benign in children compared to adults for unknown reasons. This contrasts with viruses such as influenza where disease manifestations are often more severe in children1. We hypothesized that a more robust early innate immune response to SARS-CoV-2 may protect against severe disease and compared clinical outcomes, viral copies and cellular gene and protein expression in nasopharyngeal swabs from 12 children and 27 adults upon presentation to the Emergency Department. SARS-CoV-2 copies were similar, but compared to adults, children displayed higher expression of genes associated with interferon signaling, NLRP3 inflammasome, and other innate pathways. Higher levels of IFN-alpha2, IFN-gamma, IP-10, IL-8, and IL-1beta were detected in nasal fluid in children versus adults. Anti-SARS-CoV-2 IgA and IgG were detected in nasal fluid from both groups and correlated negatively with mucosal IL-18. These findings suggest that a more robust innate immune response in children compared to adults contributes to favorable clinical outcomes.

Retrospective study of the use of an influenza disease two-tiered classification system to characterize clinical severity in US children

In children <5 years, influenza is associated with higher risk of serious disease and hospitalization when compared with other age groups. Influenza vaccination reduces the risk of influenza and vaccination may attenuate the severity of disease. Recent studies in Europe suggest that classifying influenza disease as mild versus moderate-to-severe (M-S) using a novel definition may be clinically significant. We retrospectively evaluated whether this M-S definition also characterized influenza severity in a cohort of US children. We included children <18 years at Kaiser Permanente Northern California with PCR-confirmed influenza during the 2013–2014 influenza season. We classified children as M-S if they had ≥1 symptom: fever >39°C, acute otitis media, lower respiratory tract infection (LRTI), or extra-pulmonary complications; otherwise, they were classified as mild. We used multivariable log-binomial models to assess whether M-S influenza disease was associated with increased healthcare utilization. Nearly half of the 1,105 influenza positive children were classified as M-S. Children 6–35 months had the highest proportion of M-S disease (35.1%), mostly due to LRTI (63.2%) and fever (44.6%). Children ≥6 months who had M-S disease were associated with a 1.6 to 2.8 times increased likelihood of having had an emergency department or any follow-up outpatient visits. Those who had M-S disease were associated with an increased likelihood of receiving antibiotics, with the highest likelihood in children 6–35 months (RR 9.0, 95% CI 4.1, 19.8). While more studies are needed, an influenza classification system may distinguish children with more clinically significant disease.

Human genetics of life-threatening influenza pneumonitis

Influenza viruses infect millions of people around the globe annually, usually causing self-limited upper respiratory tract infections. However, a small but non-negligible proportion of patients suffer from life-threatening pulmonary disease. Those affected include otherwise healthy individuals, and children with primary infections in particular. Much effort has been devoted to virological studies of influenza and vaccine development. By contrast, the enormous interindividual variability in susceptibility to influenza has received very little attention. One interesting hypothesis is that interindividual variability is driven largely by the genetic makeup of the infected patients. Unbiased genomic approaches have been used to search for genetic lesions in children with life-threatening pulmonary influenza. Four monogenic causes of severe influenza pneumonitis—deficiencies of GATA2, IRF7, IRF9, and TLR3—have provided evidence that severe influenza pneumonitis can be genetic and often in patients with no other severe infections. These deficiencies highlight the importance of human type I and III IFN-mediated immunity for host defense against influenza. Clinical penetrance is incomplete, and the underlying mechanisms are not yet understood. However, human genetic studies have clearly revealed that seemingly sporadic and isolated life-threatening influenza pneumonitis in otherwise healthy individuals can be genetic.

Influenza A and B in a cohort of outpatient children and adolescent with influenza like-illness during two consecutive influenza seasons

INTRODUCTION

Influenza is an important cause of morbimortality worldwide. Although people at the extremes of age have a greater risk of complications, influenza has been more frequently investigated in the elderly than in children, and inpatients than outpatients. Yearly vaccination with trivalent or quadrivalent vaccines is the main strategy to control influenza.

OBJECTIVES

Determine the clinical and molecular characteristics of influenza A and B infections in children and adolescents with influenza-like illness (ILI).

METHODS

A cohort of outpatient children and adolescents with ILI was followed for 20 months. Influenza was diagnosed with commercial multiplex PCR platforms.

RESULTS

179 patients had 277 episodes of ILI, being 79 episodes of influenza A and 20 episodes of influenza B. Influenza A and B cases were mild and had similar presentation. Phylogenetic tree of influenza B viruses showed that 91.6% belonged to the B/Yamagata lineage, which is not included in trivalent vaccines.

CONCLUSIONS

Influenza A and B are often detected in children and adolescents with ILI episodes, with similar and mild presentation in outpatients. The mismatch between the circulating influenza viruses and the trivalent vaccine offered in Brazil may have contributed to the high frequency of influenza A and B in this population.

Pharmacokinetics and Pharmacodynamics of Conventional-Dose vs Triple-Dose Oseltamivir in Severely Immunocompromised Children With Influenza

This randomized phase 1b study evaluated the pharmacokinetics/pharmacodynamics of conventional-dose (30–75 mg twice daily [BID]) vs triple-dose (90–225 mg BID; weight-adjusted) oseltamivir for treatment of influenza in severely immunocompromised children <13 years. Oseltamivir carboxylate (OC) C_max and AUC_0-12h were ~2-fold higher with triple-dose vs conventional-dose oseltamivir. Increased dose/exposure of oseltamivir/OC did not improve virological outcomes or reduce viral resistance. Median time to cessation of viral shedding was similar with triple-dose and conventional-dose oseltamivir (150.7 vs 157.1 hours, respectively); median time to alleviation of baseline fever was longer with conventional-dose oseltamivir (28.4 vs 11.3 hours). No new safety signals were identified.