Racial/Ethnic Disparities in the Incidences of Bronchiolitis Requiring Hospitalization

A Review of Respiratory Syncytial Virus Epidemiology Among Children: Linking Effective Prevention to Vulnerable Populations

Respiratory syncytial virus (RSV) is the greatest contributor to lower respiratory tract infections (LRTI) in children less than 5 years of age and the leading cause for infant hospitalizations in the United States (US). The burden of severe disease disproportionately impacts racial and ethnic minority groups, highlighting the need for interventions that promote health equity. Recent advancements in effective prophylactic agents have the potential to drastically alter the landscape of RSV disease among all young children. The effectiveness of prophylaxis, however, will rely on a clear understanding of RSV epidemiology. The purpose of this review is to discuss key aspects of RSV epidemiology while focusing on efforts to support equitable distribution of prophylactic agents to mitigate existing health disparities.

Effects of infant bronchiolitis on family life

Background

Bronchiolitis is a respiratory infection of viral origin and is often linked to syncytial respiratory virus. It is the most frequent cause of hospitalisation in children aged under 2 years and sometimes requires transfer to intensive care. Infectious complications may also arise in the short term, and longer-term progression towards asthma is also possible. The occurrence of bronchiolitis in children may affect families in different ways, and may have psychological, organisational, employment-related, and possibly financial consequences.

Objective

The aim of the study was to determine the familial and socioeconomic repercussions of bronchiolitis in infants.

Setting

Parents with a child with bronchiolitis between January 2021 and May 2022, who were registered at the site of the Association Française de Pédiatrie Ambulatoire (Mpedia site) or at the site of the Malin Programme, which serves families experiencing financial difficulties, were included in the study.

Participants

All parents consenting to participate in the study.

Results

A total of 2,059 valid questionnaires were retrieved: 1,318 (64%) were obtained from parents through the Mpedia website and 741 (36%) were obtained through the Malin Programme. Parents associated with the Malin Programme had more children, as well as higher rates of unemployment and financial difficulties, and required greater medical assistance. Hospitalisation was necessary in 37% of cases and was comparable between groups. During the illness, moderate to severe anxiety was present in 73% of parents; this percentage rose to 87% if the child required hospitalisation. Many parents reported effects on daily home (84%) and work life (90%), and 60% had taken a leave of absence from work.

Conclusion

Beyond the immediate or longer-term medical consequences of bronchiolitis in infants, the illness affects families in multiple ways and can lead to anxiety, as well as changes in day-to-day home and work life. Physicians should have greater awareness of these consequences and should strive to decrease their impact.

Sociodemographic Factors and Trends in Bronchiolitis-Related Emergency Department Visit and Hospitalization Rates

Importance

Bronchiolitis is the most common and most cumulatively expensive condition in pediatric hospital care. Few population-based studies have examined health inequalities in bronchiolitis outcomes over time.

Objective

To examine trends in bronchiolitis-related emergency department (ED) visit and hospitalization rates by sociodemographic factors in a universally funded health care system.

Design, Setting, and Participants

This repeated cross-sectional cohort study was performed from April 1, 2004, to March 31, 2022, using population-based health administrative data from children younger than 2 years in Ontario, Canada.

Main Outcome and Measures

Bronchiolitis ED visit and hospitalization rates per 1000 person-years reported for the equity stratifiers of sex, residence location (rural vs urban), and material resources quintile. Trends in annual rates by equity stratifiers were analyzed using joinpoint regression and estimating the average annual percentage change (AAPC) with 95% CI and the absolute difference in AAPC with 95% CI from April 1, 2004, to March 31, 2020.

Results

Of 2 921 573 children included in the study, 1 422 088 (48.7%) were female and 2 619 139 (89.6%) lived in an urban location. Emergency department visit and hospitalization rates were highest for boys, those with rural residence, and those with least material resources. There were no significant between-group absolute differences in the AAPC in ED visits per 1000 person-years by sex (female vs male; 0.22; 95% CI, -0.92 to 1.35; P = .71), residence (rural vs urban; -0.31; 95% CI -1.70 to 1.09; P = .67), or material resources (quintile 5 vs 1; -1.17; 95% CI, -2.57 to 0.22; P = .10). Similarly, there were no significant between-group absolute differences in the AAPC in hospitalizations per 1000 person-years by sex (female vs male; 0.53; 95% CI, -1.11 to 2.17; P = .53), residence (rural vs urban; -0.62; 95% CI, -2.63 to 1.40; P = .55), or material resources (quintile 5 vs 1; -0.93; 95% CI -3.80 to 1.93; P = .52).

Conclusions and Relevance

In this population-based cohort study of children in a universally funded health care system, inequalities in bronchiolitis ED visit and hospitalization rates did not improve over time.

Personalized Infant Risk Prediction for Severe Respiratory Syncytial Virus Lower Respiratory Tract Infection Requiring Intensive Care Unit Admission

Background

Currently, there are no available tools to identify infants at the highest risk of significant morbidity and mortality from respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) who would benefit most from RSV prevention products. The objective was to develop and internally validate a personalized risk prediction tool for use among all newborns that uses readily available birth/postnatal data to predict RSV LRTI requiring intensive care unit (ICU) admission.

Methods

We conducted a population-based birth cohort study of infants born from 1995 to 2007, insured by the Tennessee Medicaid Program, and who did not receive RSV immunoprophylaxis during the first year of life. The primary outcome was severe RSV LRTI requiring ICU admission during the first year of life. We built a multivariable logistic regression model including demographic and clinical variables available at or shortly after birth to predict the primary outcome.

Results

In a population-based sample of 429 365 infants, 713 (0.2%) had severe RSV LRTI requiring ICU admission. The median age of admission was 66 days (interquartile range, 37-120). Our tool, including 19 variables, demonstrated good predictive accuracy (area under the curve, 0.78; 95% confidence interval, 0.77-0.80) and identified infants who did not qualify for palivizumab, based on American Academy of Pediatrics guidelines, but had higher predicted risk levels than infants who qualified (27% of noneligible infants with >0.16% predicted probabilities [lower quartile for eligible infants]).

Conclusions

We developed a personalized tool that identified infants at increased risk for severe RSV LRTI requiring ICU admission, expected to benefit most from immunoprophylaxis.

Association of Maternal Body Mass Index During Early Pregnancy With Offspring Lower Respiratory Infections: A Nationwide Cohort Study

OBJECTIVE

To assess whether or to what extent maternal obesity during early pregnancy could increase the risk of offspring lower respiratory infections (LRI).

STUDY DESIGN

This population-based cohort included 688,457 live singleton births born in Denmark between 2004 and 2016. The exposure was maternal body mass index (BMI) during early pregnancy, and the outcome was LRI in offspring. Cox regression models were used to estimate hazard ratios with their 95% confidence intervals (CI) for the association. We also performed subanalysis stratified by the LRI onset age, number of infection episodes before the age of 3, infection pathogens, infection sites, duration of hospital stay due to LRI and allergic constitution of children.

RESULTS

A total of 64,725 LRIs in offspring were identified during follow-up. Maternal overweight (BMI 25.0-29.9 kg/m 2 ), moderate or severe obesity (BMI 30.0-39.9 kg/m 2 ) and very severe obesity (BMI ≥40 kg/m 2 ) were associated with a 7% (95% CI: 5%-9%), 16% (95% CI: 14%-19%) and 21% (95% CI: 13%-28%) increased risk of LRI in offspring, respectively. Higher maternal BMI was positively associated with earlier onset age, more episodes before the age of 3, and longer hospital stay of LRI in offspring. In addition, allergic constitution of offspring significantly enhanced the effect of maternal BMI on offspring LRI (44% increased risk, 95% CI: 5%-97% for very severe obesity).

CONCLUSIONS

Maternal BMI during early pregnancy might be a risk factor for offspring LRI, especially in children with allergic constitution.

Epidemiology of pediatric hospitalizations at general hospitals and freestanding children's hospitals in the United States: 2019 update

BACKGROUND

General hospitals (GH) provide inpatient care for the majority of hospitalized children in the United States, yet the majority of hospital pediatrics research is conducted at freestanding children's hospitals.

OBJECTIVE

Updating a prior 2012 analysis, this study used 2019 data to describe characteristics of pediatric hospitalizations at general and freestanding hospitals in the United States and identify the most common and costly reasons for hospitalization in these settings.

DESIGNS, SETTING, AND PARTICIPANTS

This study examined hospitalizations in children <18 years using the Healthcare Cost and Utilization Project's 2019 Kids' Inpatient Database, stratifying neonatal and nonneonatal hospital stays.

INTERVENTION

Not applicable.

MAIN OUTCOME AND MEASURES

Sociodemographic and clinical differences between hospitalizations at general and freestanding children's hospitals were examined, applying survey weights to generate national estimates.

RESULTS

There were an estimated 5,263,218 pediatric hospitalizations in 2019, including 3,757,601 neonatal and 1,505,617 nonneonatal hospital stays. Overall, 88.6% (n = 4,661,288) of hospitalizations occurred at GH, including 97.6% of neonatal hospitalizations and 65.9% of nonneonatal hospitalizations. 11.4% (n = 601,930) of hospitalizations occurred at freestanding children's hospitals, including 2.4% (n = 88,313) of neonatal hospitalizations and 34.1% (n = 513,616) of nonneonatal hospitalizations. In total, 98.9% of complicated birth hospitalizations and 66.0% of neonatal nonbirth hospitalizations occurred at GH. Among nonneonatal stays, 85.2% of mental health hospitalizations, 63.5% of medical hospitalizations, and 61.3% of surgical hospitalizations occurred at GH.

Pediatric Hospitalizations at Rural and Urban Teaching and Nonteaching Hospitals in the US, 2009-2019

Importance

National analyses suggest that approximately 1 in 5 US hospitals closed their pediatric units between 2008 and 2018. The extent to which pediatric hospitalizations at general hospitals in rural and urban communities decreased during this period is not well understood.

Objective

To describe changes in the number and proportion of pediatric hospitalizations and costs at urban teaching, urban nonteaching, and rural hospitals vs freestanding children's hospitals from 2009 to 2019; to estimate the number and proportion of hospitals providing inpatient pediatric care; and to characterize changes in clinical complexity.

Design, Setting, and Participants

This study is a retrospective cross-sectional analysis of the 2009, 2012, 2016, and 2019 Kids' Inpatient Database, a nationally representative data set of US pediatric hospitalizations among children younger than 18 years. Data were analyzed from February to June 2023.

Exposures

Pediatric hospitalizations were grouped as birth or nonbirth hospitalizations. Hospitals were categorized as freestanding children's hospitals or as rural, urban nonteaching, or urban teaching general hospitals.

Main Outcomes and Measures

The primary outcomes were annual number and proportion of birth and nonbirth hospitalizations and health care costs, changes in the proportion of hospitalizations with complex diagnoses, and estimated number and proportion of hospitals providing pediatric care and associated hospital volumes. Regression analyses were used to compare health care utilization in 2019 vs that in 2009.

Results

The data included 23.2 million (95% CI, 22.7-23.6 million) weighted hospitalizations. From 2009 to 2019, estimated national annual pediatric hospitalizations decreased from 6 425 858 to 5 297 882, as birth hospitalizations decreased by 10.6% (95% CI, 6.1%-15.1%) and nonbirth hospitalizations decreased by 28.9% (95% CI, 21.3%-36.5%). Concurrently, hospitalizations with complex chronic disease diagnoses increased by 45.5% (95% CI, 34.6%-56.4%), and hospitalizations with mental health diagnoses increased by 78.0% (95% CI, 61.6%-94.4%). During this period, the most substantial decreases were in nonbirth hospitalizations at rural hospitals (4-fold decrease from 229 263 to 62 729) and urban nonteaching hospitals (6-fold decrease from 581 320 to 92 118). In 2019, birth hospitalizations occurred at 2666 hospitals. Nonbirth pediatric hospitalizations occurred at 3507 hospitals, including 1256 rural hospitals and 843 urban nonteaching hospitals where the median nonbirth hospitalization volumes were fewer than 25 per year.

Conclusions and Relevance

Between 2009 and 2019, the largest decreases in pediatric hospitalizations occurred at rural and urban nonteaching hospitals. Clinical and policy initiatives to support hospitals with low pediatric volumes may be needed to maintain hospital access and pediatric readiness, particularly in rural communities.

Effect Modification of Racial Differences in Pediatric COVID-19 Inpatient Admissions in a Large Healthcare Database

BACKGROUND

Coronavirus disease 2019 (COVID-19) has been more severe in racial and ethnic minorities relative to non-Hispanic White populations. Here, we investigate how these disparities vary across effect modifiers in a pediatric population.

METHODS

Using the TriNetX Dataworks Network from April 2020 to September 2021, we compared inpatient rates between non-Hispanic Black and non-Hispanic White patients among pediatric COVID-19 cases. Following propensity score matching, comparisons were performed within subgroups of 4 potential effect modifiers: age group (0-2, 3-5, 6-11 and 12-18 years), presence of complex comorbidities, quarter of the year (from 2020 Q2 to 2021 Q3) and geographic regions of the United States.

RESULTS

The cohort included 47,487 COVID-19 cases, of which 13,130 were Black patients. Among most subgroups of effect modifiers, inpatient rates were higher among the Black patients. The largest variation in disparities was observed across age groups and the presence of complex comorbidities. Twelve to 18 years old Black children had a 1.7% point [confidence interval (CI): 0.8-2.4] higher inpatient rate than the matched White children, whereas 0-2 years old Black children had a 2.5% point (CI: 0.9-4.1) lower rate than the matched White children. Among children with complex comorbidities, inpatient rates for Black children was 6.2 (CI: 3.4-8.9) percentage points higher than the White children; however, among kids without complex comorbidities, inpatient rates were comparable.

CONCLUSIONS

Among pediatric patients experiencing COVID-19, higher inpatient rates for Black compared with White patients were observed among older children and those with complex comorbidities. These findings can spur discussions of potential root causes of these disparities, including structural racism.

Urgent air transfers for acute respiratory infections among children from Northern Canada, 2005-2014

BACKGROUND

The incidence of hospitalizations for acute respiratory infections (ARI) among young Indigenous children from Northern Canada is consistently high. ARIs requiring urgent air transfer can be life-threatening and costly. We aimed to describe their epidemiology, estimate age-specific incidences, and explore factors associated with level of care required.

METHODS

We undertook a retrospective cohort study of children <5 years old from Northern Canada transferred by urgent air transport for ARI from 2005 through 2014 to 5 pediatric tertiary care centers in Vancouver, Edmonton, Winnipeg, Ottawa and Montreal. Admissions were identified via ARI-related ICD-9/10 coding and forward sortation area. Descriptive statistics and univariable analyses were performed.

RESULTS

Among 650 urgent air transfers, the majority were from Nunavut (n = 349, 53.7%) or Nunavik (n = 166, 25.5%), <6 months old (n = 372, 57.2%), and without underlying comorbidity (n = 458; 70.5%). Estimated annual tertiary care ARI admission rates in infants <1 year old from Nunavut (40.7/1000) and Nunavik (44.5/1000) were tenfold higher than in children aged 1 to 4 years. Bronchiolitis (n = 333, 51.2%) and pneumonia (n = 208, 32.0%) were the most common primary discharge diagnoses. Nearly half required critical care (n = 316, 48.6%); mechanical ventilation rates ranged from 7.2% to 55.9% across centres. The most common primary pathogen was respiratory syncytial virus (n = 196, 30.1%). Influenza A or B was identified in 35 cases (5.4%) and vaccine-preventable bacterial infections in 27 (4.1%) cases.

INTERPRETATION

Urgent air transfers for ARI from Northern Canada are associated with high acuity. Variations in levels of care were seen across referral centers, age groups and pathogens.

Stakeholder Perspectives on Hospitalization Decisions and Shared Decision-Making in Bronchiolitis

OBJECTIVES

Our objective was to elicit clinicians' and parents' perspectives about decision-making related to hospitalization for children with bronchiolitis and the use of shared decision-making (SDM) to guide these decisions.

METHODS

We conducted individual, semistructured interviews with purposively sampled clinicians (pediatric emergency medicine physicians and nurses) at 2 children's hospitals and parents of children age <2 years with bronchiolitis evaluated in the emergency department at 1 hospital. Interviews elicited clinicians' and parents' perspectives on decision-making and SDM for bronchiolitis. We conducted an inductive analysis following the principles of grounded theory until data saturation was reached for both groups.

RESULTS

We interviewed 24 clinicians (17 physicians, 7 nurses) and 20 parents. Clinicians identified factors in 3 domains that contribute to hospitalization decision-making for children with bronchiolitis: demographics, clinical factors, and social-emotional factors. Although many clinicians supported using SDM for hospitalization decisions, most reported using a clinician-guided decision-making process in practice. Clinicians also identified several barriers to SDM, including the unpredictable course of bronchiolitis, perceptions of parents' preferences for engaging in SDM, and parents' emotions, health literacy, preferred language, and comfort with discharge. Parents wanted the opportunity to express their opinions during decision-making about hospitalization, although they often felt comfortable with the clinician's decision when adequately informed.

CONCLUSIONS

Although clinicians and parents of children with bronchiolitis are supportive of SDM, most hospitalization decision-making is clinician guided. Future investigation should evaluate how to address barriers and implement SDM in practice, including training clinicians in this SDM approach.

Disparities in COVID-19 Outcomes by Race, Ethnicity, and Socioeconomic Status: A Systematic-Review and Meta-analysis

IMPORTANCE

COVID-19 has disproportionately affected racial and ethnic minority groups, and race and ethnicity have been associated with disease severity. However, the association of socioeconomic determinants with racial disparities in COVID-19 outcomes remains unclear.

OBJECTIVE

To evaluate the association of race and ethnicity with COVID-19 outcomes and to examine the association between race, ethnicity, COVID-19 outcomes, and socioeconomic determinants.

DATA SOURCES

A systematic search of PubMed, medRxiv, bioRxiv, Embase, and the World Health Organization COVID-19 databases was performed for studies published from January 1, 2020, to January 6, 2021.

STUDY SELECTION

Studies that reported data on associations between race and ethnicity and COVID-19 positivity, disease severity, and socioeconomic status were included and screened by 2 independent reviewers. Studies that did not have a satisfactory quality score were excluded. Overall, less than 1% (0.47%) of initially identified studies met selection criteria.

DATA EXTRACTION AND SYNTHESIS

Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. Associations were assessed using adjusted and unadjusted risk ratios (RRs) and odds ratios (ORs), combined prevalence, and metaregression. Data were pooled using a random-effects model.

MAIN OUTCOMES AND MEASURES

The main measures were RRs, ORs, and combined prevalence values.

RESULTS

A total of 4 318 929 patients from 68 studies were included in this meta-analysis. Overall, 370 933 patients (8.6%) were African American, 9082 (0.2%) were American Indian or Alaska Native, 101 793 (2.4%) were Asian American, 851 392 identified as Hispanic/Latino (19.7%), 7417 (0.2%) were Pacific Islander, 1 037 996 (24.0%) were White, and 269 040 (6.2%) identified as multiracial and another race or ethnicity. In age- and sex-adjusted analyses, African American individuals (RR, 3.54; 95% CI, 1.38-9.07; P = .008) and Hispanic individuals (RR, 4.68; 95% CI, 1.28-17.20; P = .02) were the most likely to test positive for COVID-19. Asian American individuals had the highest risk of intensive care unit admission (RR, 1.93; 95% CI, 1.60-2.34, P < .001). The area deprivation index was positively correlated with mortality rates in Asian American and Hispanic individuals (P < .001). Decreased access to clinical care was positively correlated with COVID-19 positivity in Hispanic individuals (P < .001) and African American individuals (P < .001).

CONCLUSIONS AND RELEVANCE

In this study, members of racial and ethnic minority groups had higher risks of COVID-19 positivity and disease severity. Furthermore, socioeconomic determinants were strongly associated with COVID-19 outcomes in racial and ethnic minority populations.

Racial and ethnic disparities in bronchiolitis management in freestanding children's hospitals

OBJECTIVE

Variation in bronchiolitis management by race and ethnicity within emergency departments (EDs) has been described in single-center and prospective studies, but large-scale assessments across EDs and inpatient settings are lacking. Our objective is to describe the association between race and ethnicity and bronchiolitis management across 37 U.S. freestanding children's hospitals from 2015 to 2018.

METHODS

Using the Pediatric Health Information System, we analyzed ED and inpatient visits from November 2015 to November 2018 of children with bronchiolitis 3 to 24 months old. Rates of use for specific diagnostic tests and therapeutic measures were compared across the following race/ethnicity categories: 1) non-Hispanic White (NHW), 2) non-Hispanic Black (NHB), 3) Hispanic, and 4) other. The subanalyses of ED patients only and children < 1 year old were performed. Mixed-effect logistic regression was performed to compare the adjusted odds of receiving specific test/treatment using NHW children as the reference group.

RESULTS

A total of 134,487 patients met inclusion criteria (59% male, 28% NHB, 26% Hispanic). Adjusted analysis showed that NHB children had higher odds of receiving medication associated with asthma (odds ratio [OR] = 1.27, 95% confidence interval [CI] = 1.22 to 1.32) and lower odds of receiving diagnostic tests (blood cultures, complete blood counts, viral testing, chest x-rays; OR = 0.78, 95% CI = 0.75 to 0.81) and antibiotics (OR = 0.58, 95% CI = 0.52 to 0.64) than NHW children. Hispanic children had lower odds of receiving diagnostic testing (OR = 0.94, 95% CI = 0.90 to 0.98), asthma-associated medication (OR = 0.92, 95% CI = 0.88 to 0.96), and antibiotics (OR = 0.74, 95% CI = 0.66 to 0.82) compared to NHW children.

CONCLUSION

NHB children more often receive corticosteroid and bronchodilator therapies; NHW children more often receive antibiotics and chest radiography. Given that current guidelines generally recommend supportive care with limited diagnostic testing and medical intervention, these findings among NHB and NHW children represent differing patterns of overtreatment. The underlying causes of these patterns require further investigation.

Maternal pre-pregnancy weight and early life lower respiratory tract infections in a low-income urban minority birth cohort

The prevalence of maternal obesity has increased dramatically with adverse consequences on infant health. Prior studies have reported associations between maternal obesity and childhood wheeze, asthma as well as lower respiratory tract infections (LRTI). However, studies examining the association of obesity with early-life LRTIs in low-income urban minority populations are still lacking. This is a critical gap because both obesity and infant respiratory morbidity are more prevalent and severe in these communities. We examined mother-child dyads from the Boston Birth Cohort (BBC) to define the longitudinal association of maternal pre-pregnancy BMI and LRTI in infancy, defined as the presence of bronchiolitis, bronchitis, or pneumonia during the first year of life (< 12 months of age). A total of 2,790 mother-child dyads were included in our analyses. Infants born to pre-pregnancy obese mothers (n = 688, 25%) had 1.43 increased odds (adjOR = 1.43, 95% CI 1.08-1.88, p = 0.012) of developing LRTI during the first year of life when compared with newborns born to normal-weight mothers after adjusting by relevant LRTI risk factors. Notably, infants born to overweight mothers (n = 808, 29%) followed a similar trend (adjOR = 1.31, 95% CI 1.00-1.72, p = 0.048). Our study demonstrated that maternal pre-pregnancy obesity is an independent risk factor for the development of LRTI during infancy in a low-income urban minority birth cohort.

Airway mir-155 responses are associated with TH1 cytokine polarization in young children with viral respiratory infections

BACKGROUND

MicroRNAs (miRs) control gene expression and the development of the immune system and antiviral responses. MiR-155 is an evolutionarily-conserved molecule consistently induced during viral infections in different cell systems. Notably, there is still an unresolved paradox for the role of miR-155 during viral respiratory infections. Despite being essential for host antiviral TH1 immunity, miR-155 may also contribute to respiratory disease by enhancing allergic TH2 responses and NFkB-mediated inflammation. The central goal of this study was to define how airway miR-155 production is related to TH1, TH2, and pro-inflammatory cytokine responses during naturally occurring viral respiratory infections in young children.

METHODS

Normalized nasal airway levels of miR-155 and nasal protein levels of IFN-γ, TNF-α, IL-1β, IL-13, IL-4 were quantified in young children (≤2 years) hospitalized with viral respiratory infections and uninfected controls. These data were linked to individual characteristics and respiratory disease parameters.

RESULTS

A total of 151 subjects were included. Increased miR-155 levels were observed in nasal samples from patients with rhinovirus, RSV and all respiratory viruses analyzed. High miR-155 levels were strongly associated with high IFN-γ production, increased airway TH1 cytokine polarization (IFN-γ/IL-4 ratios) and increased pro-inflammatory responses. High airway miR-155 levels were linked to decreased respiratory disease severity in individuals with high airway TH1 antiviral responses.

CONCLUSIONS

The airway secretion of miR-155 during viral respiratory infections in young children is associated with enhanced antiviral immunity (TH1 polarization). Further studies are needed to define additional physiological roles of miR-155 in the respiratory tract of human infants and young children during health and disease.