Clinical Features and Outcomes of Immunocompromised Children Hospitalized With Laboratory-Confirmed Influenza in the United States, 2011-2015

Association of Chronic Medical Conditions With Severe Outcomes Among Nonpregnant Adults 18-49 Years Old Hospitalized With Influenza, FluSurv-NET, 2011-2019

Background

Older age and chronic conditions are associated with severe influenza outcomes; however, data are only comprehensively available for adults ≥65 years old. Using data from the Influenza Hospitalization Surveillance Network (FluSurv-NET), we identified characteristics associated with severe outcomes in adults 18-49 years old hospitalized with influenza.

Methods

We included FluSurv-NET data from nonpregnant adults 18-49 years old hospitalized with laboratory-confirmed influenza during the 2011-2012 through 2018-2019 seasons. We used bivariate and multivariable logistic regression to determine associations between select characteristics and severe outcomes including intensive care unit (ICU) admission, invasive mechanical ventilation (IMV), and in-hospital death.

Results

A total of 16 140 patients aged 18-49 years and hospitalized with influenza were included in the analysis; the median age was 39 years, and 26% received current-season influenza vaccine before hospitalization. Obesity, asthma, and diabetes mellitus were the most common chronic conditions. Conditions associated with a significantly increased risk of severe outcomes included age group 30-39 or 40-49 years (IMV, age group 30-39 years: adjusted odds ratio [aOR], 1.25; IMV, age group 40-49 years: aOR, 1.36; death, age group 30-39 years: aOR, 1.28; death, age group 40-49 years: aOR, 1.69), being unvaccinated (ICU: aOR, 1.18; IMV: aOR, 1.25; death: aOR, 1.48), and having chronic conditions including extreme obesity and chronic lung, cardiovascular, metabolic, neurologic, or liver diseases (ICU: range aOR, 1.22-1.56; IMV: range aOR, 1.17-1.54; death: range aOR, 1.43-2.36).

Conclusions

To reduce the morbidity and mortality associated with influenza among adults aged 18-49 years, health care providers should strongly encourage receipt of annual influenza vaccine and lifestyle/behavioral modifications, particularly among those with chronic medical conditions.

Outcomes of immunocompromised children hospitalized for influenza, 2010-2021, the Canadian Immunization Monitoring program active (IMPACT)

OBJECTIVES

To evaluate immunocompromising conditions and subgroups of immunocompromise as risk factors for severe outcomes among children admitted for influenza.

METHODS

We performed active surveillance for laboratory-confirmed influenza hospitalizations among children ≤16 years old at the 12 Canadian Immunization Monitoring Program Active hospitals, during 2010-2021. Logistic regression analyses were used to compare outcomes between immunocompromised and non-immunocompromised children, and for different subgroups of immunocompromise. The primary outcome was intensive care unit (ICU) admission; secondary outcomes were mechanical ventilation and death.

RESULTS

Among 8982 children, 892 (9.9%) were immunocompromised; these patients were older (median 5.6 [IQR 3.1 - 10.0] vs 2.4 [1 -6] years, p<0.001) than non-immunocompromised children, had similar frequency of comorbidities excluding immunocompromise and/or malignancy (38% [340/892) vs 40% [3272/8090], p=0.2), but fewer respiratory symptoms, such as respiratory distress (20% [177/892] vs 42% [3424/8090], p<0.001). In multivariable analyses, immunocompromise (adjusted odds ratio [aOR] 0.19, 95% CI 0.14-0.25) and its subcategories immunodeficiency (aOR 0.16, 95% CI 0.10-0.23), immunosuppression (aOR 0.17, 95% CI 0.12-0.23), chemotherapy (aOR 0.07, 95% CI 0.03-0.13) and solid organ transplantation (aOR 0.17, 95% CI 0.06-0.37) were associated with decreased probability of ICU admission in children admitted for influenza. Immunocompromise was also associated with decreased probability for mechanical ventilation (aOR 0.26, 95% CI 0.16-0.38) or death (aOR 0.22, 95% CI 0.03-0.72).

CONCLUSIONS

Immunocompromised children are overrepresented among hospitalizations for influenza, but have decreased probability of ICU admission, mechanical ventilation, and mortality following admission. Admission bias precludes generalizability beyond the hospital setting.

Incidence of and risk factors for influenza-associated hospital encounters in pediatric solid organ transplant recipients

Few studies have defined the incidence of and risk factors for influenza infection in pediatric solid organ transplant (SOT) recipients. We used a linkage between the Pediatric Health Information System and the Scientific Registry of Transplant Recipients databases to identify posttransplant influenza-associated hospital encounters (IAHEs) in pediatric SOT recipients of single-organ transplants. Among 7997 unique pediatric SOT recipients transplanted between January 01, 2006, and January 06, 2016, estimated 1- and 3-year posttransplant cumulative incidence rates of IAHEs were 2.7% (95% CI, 2.4%-3.1%) and 7.4% (95% CI, 6.8%-8.0%), respectively. One- and 3-year cumulative incidence rates of severe IAHEs were 0.3% (95% CI, 0.2%-0.5%) and 0.9% (95% CI, 0.7%-1.2%), respectively. Multivariable analysis showed that the organ type (adjusted subdistribution hazard ratio [aSHR]-kidney: reference, liver: 0.64 [95% CI, 0.49-0.84], and heart: 0.72 [95% CI, 0.57-0.93]), race/ethnicity (aSHR-non-Hispanic White: reference, non-Hispanic Black: 1.63 [95% CI, 1.29-2.07], Hispanic 1.57 [95% CI, 1.27-1.94]), and increasing age at transplant (aSHR, 0.93 [95% CI, 0.91-0.94]) were significantly associated with IAHE occurrence. Heart transplant recipients had a near statistically significant increase in hazard for severe IAHE (aSHR 1.96 [0.92-3.49]). Our findings may help guide future influenza prevention efforts and facilitate intervention impact assessment measurement in pediatric SOT recipients.

Predictors of unfavorable outcome in children hospitalized with influenza and differences in clinical presentation among serotypes

BACKGROUND

Apart from age and underlying disease, predictors of adverse outcome in children hospitalized with influenza are poorly understood.

OBJECTIVES

Our goal is to determine clinical and laboratory predictors that help identify children at increased risk for an unfavorable course and identify differences in clinical presentation between serotypes.

STUDY DESIGN

A retrospective, observational cohort study conducted at the Rambam Healthcare Campus in Haifa. We analyzed data from electronic records of children < 18 years with influenza A or B infection hospitalized between 2009 and 2020. Multivariate regression analyses were used to identify predictors of unfavorable outcome, defined as mortality, ICU admission, intubation, prolonged length of stay, or bacterial coinfection.

RESULTS

A total of 1077 children were included, of whom 54% were male. The median age was 2.5 years. Influenza A was detected in 797 (74%) and influenza B in 286 (26%) of the cases. Children with influenza A were younger (OR 2.51, 95%CI 1.90-3.33), more likely to have oxygen desaturation <90% (OR 2.44, 95%CI 1.23-4.83) and an elevated CRP>5 mg/dL on admission (OR 2.67, 95% CI 1.63-4.37). In multivariate analyses, oxygen desaturation <90% and CRP > 5 mg/dL at admission had an 11.1 and 4-fold increased risk of unfavorable outcome, respectively, in addition to a 3.1 and 1.6-fold increased risk in the presence of underlying condition or influenza A serotype infection, respectively.

CONCLUSIONS

Data available on admission can help identify children hospitalized with influenza who are at increased risk for complications and unfavorable outcome, encouraging aggressive treatment and care.

Epidemiology, Clinical Characteristics, and Outcomes of Influenza-Associated Hospitalizations in US Children Over 9 Seasons Following the 2009 H1N1 Pandemic

BACKGROUND

Recent population-based data are limited regarding influenza-associated hospitalizations in US children.

METHODS

We identified children <18 years hospitalized with laboratory-confirmed influenza during 2010-2019 seasons, through the Centers for Disease Control and Prevention's Influenza Hospitalization Surveillance Network. Adjusted hospitalization and in-hospital mortality rates were calculated, and multivariable logistic regression was conducted to evaluate risk factors for pneumonia, intensive care unit (ICU) admission, mechanical ventilation, and death.

RESULTS

Over 9 seasons, adjusted influenza-associated hospitalization incidence rates ranged from 10 to 375 per 100 000 persons each season and were highest among infants <6 months old. Rates decreased with increasing age. The highest in-hospital mortality rates were observed in children <6 months old (0.73 per 100 000 persons). Over time, antiviral treatment significantly increased, from 56% to 85% (P < .001), and influenza vaccination rates increased from 33% to 44% (P = .003). Among the 13 235 hospitalized children, 2676 (20%) were admitted to the ICU, 2262 (17%) had pneumonia, 690 (5%) required mechanical ventilation, and 72 (0.5%) died during hospitalization. Compared with those <6 months of age, hospitalized children ≥13 years old had higher odds of pneumonia (adjusted odds ratio, 2.7 [95% confidence interval, 2.1-3.4], ICU admission (1.6 [1.3-1.9]), mechanical ventilation (1.6 [1.1-2.2]), and death (3.3 [1.2-9.3]).

CONCLUSIONS

Hospitalization and death rates were greatest in younger children at the population level. Among hospitalized children, however, older children had a higher risk of severe outcomes. Continued efforts to prevent and attenuate influenza in children are needed.

Recent Progress in Recombinant Influenza Vaccine Development Toward Heterosubtypic Immune Response

Flu, a viral infection caused by the influenza virus, is still a global public health concern with potential to cause seasonal epidemics and pandemics. Vaccination is considered the most effective protective strategy against the infection. However, given the high plasticity of the virus and the suboptimal immunogenicity of existing influenza vaccines, scientists are moving toward the development of universal vaccines. An important property of universal vaccines is their ability to induce heterosubtypic immunity, i.e., a wide immune response coverage toward different influenza subtypes. With the increasing number of studies and mounting evidence on the safety and efficacy of recombinant influenza vaccines (RIVs), they have been proposed as promising platforms for the development of universal vaccines. This review highlights the current progress and advances in the development of RIVs in the context of heterosubtypic immunity induction toward universal vaccine production. In particular, this review discussed existing knowledge on influenza and vaccine development, current hemagglutinin-based RIVs in the market and in the pipeline, other potential vaccine targets for RIVs (neuraminidase, matrix 1 and 2, nucleoprotein, polymerase acidic, and basic 1 and 2 antigens), and deantigenization process. This review also provided discussion points and future perspectives in looking at RIVs as potential universal vaccine candidates for influenza.

Risk Factors for Severe COVID-19 in Children

OBJECTIVES

Describe population-based rates and risk factors for severe coronavirus disease 2019 (COVID-19) (ie, ICU admission, invasive mechanical ventilation, or death) among hospitalized children.

METHODS

During March 2020 to May 2021, the COVID-19-Associated Hospitalization Surveillance Network identified 3106 children hospitalized with laboratory-confirmed severe acute respiratory syndrome coronavirus 2 infection in 14 states. Among 2293 children primarily admitted for COVID-19, multivariable generalized estimating equations generated adjusted risk ratios (aRRs) and 95% confidence intervals (CIs) of the associations between demographic and medical characteristics abstracted from medical records and severe COVID-19. We calculated age-adjusted cumulative population-based rates of severe COVID-19 among all children.

RESULTS

Approximately 30% of hospitalized children had severe COVID-19; 0.5% died during hospitalization. Among hospitalized children aged <2 years, chronic lung disease (aRR: 2.2; 95% CI: 1.1-4.3), neurologic disorders (aRR: 2.0; 95% CI: 1.5‒2.6), cardiovascular disease (aRR: 1.7; 95% CI: 1.2‒2.3), prematurity (aRR: 1.6; 95% CI: 1.1‒2.2), and airway abnormality (aRR: 1.6; 95% CI: 1.1‒2.2) were associated with severe COVID-19. Among hospitalized children aged 2 to 17 years, feeding tube dependence (aRR: 2.0; 95% CI: 1.5‒2.5), diabetes mellitus (aRR: 1.9; 95% CI: 1.6‒2.3) and obesity (aRR: 1.2; 95% CI: 1.0‒1.4) were associated with severe COVID-19. Severe COVID-19 occurred among 12.0 per 100 000 children overall and was highest among infants, Hispanic children, and non-Hispanic Black children.

CONCLUSIONS

Results identify children at potentially higher risk of severe COVID-19 who may benefit from prevention efforts, including vaccination. Rates establish a baseline for monitoring changes in pediatric illness severity after increased availability of COVID-19 vaccines and the emergence of new variants.

A Retrospective Test-Negative Case-Control Study to Evaluate Influenza Vaccine Effectiveness in Preventing Hospitalizations in Children

BACKGROUND

Vaccination is the primary strategy to reduce influenza burden. Influenza vaccine effectiveness (VE) can vary annually depending on circulating strains.

METHODS

We used a test-negative case-control study design to estimate influenza VE against laboratory-confirmed influenza-related hospitalizations among children (aged 6 months-17 years) across 5 influenza seasons in Atlanta, Georgia, from 2012-2013 to 2016-2017. Influenza-positive cases were randomly matched to test-negative controls based on age and influenza season in a 1:1 ratio. We used logistic regression models to compare odds ratios (ORs) of vaccination in cases to controls. We calculated VE as [100% × (1 - adjusted OR)] and computed 95% confidence intervals (CIs) around the estimates.

RESULTS

We identified 14 596 hospitalizations of children who were tested for influenza using the multiplex respiratory molecular panel; influenza infection was detected in 1017 (7.0%). After exclusions, we included 512 influenza-positive cases and 512 influenza-negative controls. The median age was 5.9 years (interquartile range, 2.7-10.3), 497 (48.5%) were female, 567 (55.4%) were non-Hispanic Black, and 654 (63.9%) children were unvaccinated. Influenza A accounted for 370 (72.3%) of 512 cases and predominated during all 5 seasons. The adjusted VE against influenza-related hospitalizations during 2012-2013 to 2016-2017 was 51.3% (95% CI, 34.8% to 63.6%) and varied by season. Influenza VE was 54.7% (95% CI, 37.4% to 67.3%) for influenza A and 37.1% (95% CI, 2.3% to 59.5%) for influenza B.

CONCLUSIONS

Influenza vaccination decreased the risk of influenza-related pediatric hospitalizations by >50% across 5 influenza seasons.

Immunopathological similarities between COVID-19 and influenza: Investigating the consequences of Co-infection

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been a global public health emergency since December 2019, and so far, more than 980,000 people (until September 24, 2020) around the world have died. SARS-CoV-2 mimics the influenza virus regarding methods and modes of transmission, clinical features, related immune responses, and seasonal coincidence. Accordingly, co-infection by these viruses is imaginable because some studies have reported several cases with SARS-CoV-2 and influenza virus co-infection. Given the importance of the mentioned co-infection and the coming influenza season, it is essential to recognize the similarities and differences between the symptoms, immunopathogenesis and treatment of SARS-CoV-2 and influenza virus. Therefore, we reviewed the virology, clinical features, and immunopathogenesis of both influenza virus and SARS-CoV-2 and evaluated outcomes in cases with SARS-CoV-2 and influenza virus co-infection.

Co-infection of SARS-COV-2 and Influenza A Virus: A Case Series and Fast Review

Coronavirus disease 2019 (COVID-19) occurs in the influenza season and has become a global pandemic. The present study aimed to examine severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) co-infection with influenza A virus (IAV) in an attempt to provide clues for the antiviral interventions of co-infected patients. We described two patients who were co-infected with SARS-CoV-2 and IAV treated at Wuhan Union Hospital, China. In addition, we performed a review in PubMed, Web of Science and CNKI (from January 1 up to November 1, 2020) with combinations of the following key words: “COVID-19, SARS-COV-2, influenza A and co-infection”. A total of 28 co-infected patients were enrolled in the analysis. Of the 28 patients, the median age was 54.5 years (IQR, 34.25–67.5) and 14 cases (50.0%) were classified as severe types. The most common symptoms were fever (85.71%), cough (82.14%) and dyspnea (60.71%). Sixteen patients had lymphocytopenia on admission and 23 patients exhibited abnormal radiological changes. The median time from symptom onset to hospital admission was 4 days (IQR, 3–6), and the median time of hospital stay was 14 days (IQR, 8.5–16.75). In conclusion, patients with SARS-COV-2 and IAV co-infection were similar to those infected with SARS-COV-2 alone in symptoms and radiological images. SARS-COV-2 co-infection with IAV could lead to more severe clinical condition but did not experience longer hospital stay compared with patients infected with SARS-COV-2 alone.

Outcomes of Immunocompromised Adults Hospitalized With Laboratory-confirmed Influenza in the United States, 2011-2015

BACKGROUND

Hospitalized immunocompromised (IC) adults with influenza may have worse outcomes than hospitalized non-IC adults.

METHODS

We identified adults hospitalized with laboratory-confirmed influenza during 2011-2015 seasons through CDC's Influenza Hospitalization Surveillance Network. IC patients had human immunodefiency virus (HIV)/AIDS, cancer, stem cell or organ transplantation, nonsteroid immunosuppressive therapy, immunoglobulin deficiency, asplenia, and/or other rare conditions. We compared demographic and clinical characteristics of IC and non-IC adults using descriptive statistics. Multivariable logistic regression and Cox proportional hazards models controlled for confounding by patient demographic characteristics, pre-existing medical conditions, influenza vaccination, and other factors.

RESULTS

Among 35 348 adults, 3633 (10%) were IC; cancer (44%), nonsteroid immunosuppressive therapy (44%), and HIV (18%) were most common. IC patients were more likely than non-IC patients to have received influenza vaccination (53% vs 46%; P < .001), and ~85% of both groups received antivirals. In multivariable analysis, IC adults had higher mortality (adjusted odds ratio [aOR], 1.46; 95% confidence interval [CI], 1.20-1.76). Intensive care was more likely among IC patients 65-79 years (aOR, 1.25; 95% CI, 1.06-1.48) and those >80 years (aOR, 1.35; 95% CI, 1.06-1.73) compared with non-IC patients in those age groups. IC patients were hospitalized longer (adjusted hazard ratio of discharge, 0.86; 95% CI, .83-.88) and more likely to require mechanical ventilation (aOR, 1.19; 95% CI, 1.05-1.36).

CONCLUSIONS

Substantial morbidity and mortality occurred among IC adults hospitalized with influenza. Influenza vaccination and antiviral administration could be increased in both IC and non-IC adults.

Hospitalization Rates and Characteristics of Children Aged <18 Years Hospitalized with Laboratory-Confirmed COVID-19 - COVID-NET, 14 States, March 1-July 25, 2020

Most reported cases of coronavirus disease 2019 (COVID-19) in children aged <18 years appear to be asymptomatic or mild (1). Less is known about severe COVID-19 illness requiring hospitalization in children. During March 1-July 25, 2020, 576 pediatric COVID-19 cases were reported to the COVID-19-Associated Hospitalization Surveillance Network (COVID-NET), a population-based surveillance system that collects data on laboratory-confirmed COVID-19-associated hospitalizations in 14 states (2,3). Based on these data, the cumulative COVID-19-associated hospitalization rate among children aged <18 years during March 1-July 25, 2020, was 8.0 per 100,000 population, with the highest rate among children aged <2 years (24.8). During March 21-July 25, weekly hospitalization rates steadily increased among children (from 0.1 to 0.4 per 100,000, with a weekly high of 0.7 per 100,000). Overall, Hispanic or Latino (Hispanic) and non-Hispanic black (black) children had higher cumulative rates of COVID-19-associated hospitalizations (16.4 and 10.5 per 100,000, respectively) than did non-Hispanic white (white) children (2.1). Among 208 (36.1%) hospitalized children with complete medical chart reviews, 69 (33.2%) were admitted to an intensive care unit (ICU); 12 of 207 (5.8%) required invasive mechanical ventilation, and one patient died during hospitalization. Although the cumulative rate of pediatric COVID-19-associated hospitalization remains low (8.0 per 100,000 population) compared with that among adults (164.5),* weekly rates increased during the surveillance period, and one in three hospitalized children were admitted to the ICU, similar to the proportion among adults. Continued tracking of SARS-CoV-2 infections among children is important to characterize morbidity and mortality. Reinforcement of prevention efforts is essential in congregate settings that serve children, including childcare centers and schools.

The burden of laboratory-confirmed influenza infection in Lebanon between 2008 and 2016: a single tertiary care center experience

BACKGROUND

Influenza is a major cause of morbidity and mortality worldwide. Following the 2009 pandemic, there was widened interest in studying influenza burden in all regions. However, since data from the World Health Organization (WHO) Middle East and North Africa (MENA) region remain limited, we aimed to contribute to the understanding of influenza burden in Lebanon.

METHODS

A retrospective chart review extending over a period of 8 seasons from Jan 1st, 2008 till June 30th, 2016 at a tertiary care center in Beirut was performed. All cases confirmed to have influenza based on rapid antigen detection or/and polymerase chain reaction on a respiratory sample were included for analysis. Data on epidemiology, clinical presentation, complications, antiviral use and mortality were collected for analysis.

RESULTS

A total of 1829 cases of laboratory-confirmed influenza were identified. Average annual positivity rate was 14% (positive tests over total requested). Both influenza A and B co-circulated in each season with predominance of influenza A. Influenza virus started circulating in December and peaked in January and February. The age group of 19-50 years accounted for the largest proportion of cases (22.5%) followed by the age group of 5-19 years (18%). Pneumonia was the most common complication reported in 33% of cases. Mortality reached 3.8%. The two extremes of age (< 2 years and ≥ 65 years) were associated with a more severe course of disease, hospitalization, intensive care unit (ICU) admission, complications, and mortality rate. Of all the identified cases, 26% were hospitalized. Moderate-to-severe disease was more likely in influenza B cases but no difference in mortality was reported between the two types. Antivirals were prescribed in 68.8% and antibiotics in 41% of cases. There seemed to be an increasing trend in the number of diagnosed and hospitalized cases over the years of the study.

CONCLUSION

Patients with laboratory-confirmed influenza at our center had a high rate of hospitalization and mortality. A population based prospective surveillance study is needed to better estimate the burden of Influenza in Lebanon that would help formulate a policy on influenza control.

Age-Related Differences in Hospitalization Rates, Clinical Presentation, and Outcomes Among Older Adults Hospitalized With Influenza-U.S. Influenza Hospitalization Surveillance Network (FluSurv-NET)

BACKGROUND

Rates of influenza hospitalizations differ by age, but few data are available regarding differences in laboratory-confirmed rates among adults aged ≥65 years.

METHODS

We evaluated age-related differences in influenza-associated hospitalization rates, clinical presentation, and outcomes among 19 760 older adults with laboratory-confirmed influenza at 14 FluSurv-NET sites during the 2011-2012 through 2014-2015 influenza seasons using 10-year age groups.

RESULTS

There were large stepwise increases in the population rates of influenza hospitalization with each 10-year increase in age. Rates ranged from 101-417, 209-1264, and 562-2651 per 100 000 persons over 4 influenza seasons in patients aged 65-74 years, 75-84 years, and ≥85 years, respectively. Hospitalization rates among adults aged 75-84 years and ≥85 years were 1.4-3.0 and 2.2-6.4 times greater, respectively, than rates for adults aged 65-74 years. Among patients hospitalized with laboratory-confirmed influenza, there were age-related differences in demographics, medical histories, and symptoms and signs at presentation. Compared to hospitalized patients aged 65-74 years, patients aged ≥85 years had higher odds of pneumonia (aOR, 1.2; 95% CI, 1.0-1.3; P = .01) and in-hospital death or transfer to hospice (aOR, 2.1; 95% CI, 1.7-2.6; P < .01).

CONCLUSIONS

Age-related differences in the incidence and severity of influenza hospitalizations among adults aged ≥65 years can inform prevention and treatment efforts, and data should be analyzed and reported using additional age strata.