During this pandemic, the impact of health disparities on mortality due to COVID-19 has been high among our concerns about this illness.1–4 Unfortunately, disparities related to respiratory infections are not limited to COVID-19. There are decades of research revealing that morbidity and mortality are strongly influenced by the social determinants of health (SDOH).
Respiratory syncytial virus (RSV) is the leading cause of lower respiratory infection (LRI) in infants and a major cause of hospitalization in the first 2 years of life.5–7 In this issue of Pediatrics, Fitzpatrick et al8 report on the impact of sociodemographic and psychosocial factors on the risk for RSV hospitalization in children <3 years of age in Ontario, Canada. The authors used linked sociodemographic and health administrative data sets covering the period from 2012 to 2018 to identify factors associated with hospitalization. Their findings reveal the increased risk of hospitalization associated with maternal characteristics consistent with social vulnerability, including younger age, involvement with the criminal justice system, and mental health problems or addiction. The use of low-income drug benefits, a measure of socioeconomic status, was also associated with RSV hospitalization, as was an area level measure of income showing an increased risk of hospitalization with the lowest two quartiles of income.
In their study, Fitzpatrick et al8 reinforce the important, enduring, and widespread influence of SDOH on our youngest patients. These data add to the existing literature by identifying associations between hospitalization for respiratory disease in infants and specific sociodemographic factors as well as including findings from Ontario, Canada. Unfortunately, these data also confirm reports that stretch back for several decades linking SDOH with respiratory disease in infants. McConnochie et al9 used census and hospital discharge data from New York state to investigate variations in hospitalization rates for LRI in infants from 1985 to 1991. LRI hospitalization rates were significantly associated with the unemployment rate of an area in the full state analysis. When limited to Monroe County, New York, the LRI hospitalization rate increased notably from the suburban to the inner-city zip codes with a corresponding increase in measures of poverty.
The association between hospitalization for acute respiratory infections and bronchiolitis in infants with sociodemographic characteristics associated with deprivation, such as measures of overcrowding, home ownership, and unemployment, has also been shown in studies conducted from the early 1990s to 2015 in England and New Zealand.10–12 Despite the long-standing recognition of these associations, Fitzpatrick et al8 identify specific psychosocial and sociodemographic factors that impact infant hospitalization rates for acute respiratory infections and highlight the intractable nature of the SDOH effect on health and health care use.
Hospitalization is often used as a proxy measure for RSV disease severity because of the variable nature of the respiratory symptoms over time, leading to the difficulty in determining illness severity. Although the use of pulse oximetry provides an objective measure of oxygenation, several other clinical factors are often used to determine the need for hospitalization. Maternal psychosocial characteristics and prenatal health care usage patterns have been associated with rehospitalization in an infant Medicaid population, confirming that social factors impact health care providers’ decisions on hospitalization.13 The report by Fitzpatrick et al8 does not allow a determination to be made between the need for hospitalization due to RSV disease severity and the concern for the family’s ability to care for a child with symptomatic RSV disease, regardless of severity. This distinction is important when contemplating ways to decrease hospitalization due to RSV infection in infants.
In a recent publication, researchers examined child, family, and health care risk factors for RSV hospitalization in infants and toddlers in the first 3 years of life in Scotland.14 Population-attributable fractions for each significant risk factor were calculated. A reduction in hospitalization of 34% was predicted by eliminating the risk from older siblings in the home. This factor was associated with the largest impact on hospitalization, with the presence of chronic conditions (6.5%), maternal smoking (5.9%), and delayed vaccinations (2.5%) all substantially less. Fitzpatrick et al8 also reported population-attributable fractions for RSV hospitalization. They confirmed that interventions aimed at decreasing the risk of RSV disease in young infants and infants with older siblings could prevent a large percentage of hospitalizations (45.5% and 41.6%, respectively). A 7% decrease in RSV hospitalizations was predicted by removing the risk associated with living in lower income neighborhoods. Attributable risks due to maternal mental health problems and or addiction and involvement with the criminal justice system were statistically significant but impacted <1% of admissions. These data reinforce the importance of infant and family characteristics in determining RSV hospitalization, specifically young age during the RSV season and the presence of older siblings.
We know that RSV LRI is a major reason for hospital admission in the first year of life. Additionally, a large majority of infants admitted to the hospital because of RSV LRI are previously healthy term infants. Fitzpatrick et al8 reveal that the largest population level impact for reducing infant hospitalizations due to RSV would be to protect the youngest infants and those with siblings at home.
Thankfully, research into the prevention of RSV disease continues to move forward. Efforts aimed at protecting the neonate and young infant by passive immunization via maternal vaccination or with enhanced, long half-life monoclonal antibodies that could be given to all newborns in their first RSV season have been recently described.15,16 Programs under development for immunizing older infants and siblings also show promise.17
Do these advances point to a way forward? Although disparities in vaccination rates have been identified on the bases of measures of social vulnerability, national vaccination coverage rates in the United States for children remain high and stable.18 Additionally, various interventions aimed at reducing gaps in vaccination coverage based on race and income levels have shown substantial promise.19–21 Widespread vaccination was the greatest public health advance of the last century. We are looking forward to an even better future in which successful vaccine and preventive strategies targeted against RSV are widely disseminated with equal access for all our children.
Opinions expressed in these commentaries are those of the author and not necessarily those of the American Academy of Pediatrics or its Committees.
COMPANION PAPER: A companion to this article can be found online at www.pediatrics.org/cgi/doi/10.1542/2020-029090.
FUNDING: No external funding.
POTENTIAL CONFLICT OF INTEREST: Dr Caserta has received funding from Pfizer for RSV vaccine studies and from Merck for RSV epidemiology studies. Drs Caserta and Walsh have received funding for an RSV vaccine trial sponsored by the National Institute of Allergy and Infectious Diseases via a subcontract from Johns Hopkins University. All compensation for these trials is provided to the University of Rochester. Dr Walsh also has funding from Pfizer for RSV and COVID-19 vaccine studies and from Merck for RSV and coronavirus disease epidemiology studies.
FINANCIAL DISCLOSURE: The authors have indicated they have no financial relationships relevant to this article to disclose.