Study Shows Notable Age-Specific Risk Factors for Severe RSV Infection in Children

Respiratory syncytial virus (RSV) leads to about 2.1 million outpatient visits, 58,000 to 80,000 hospitalizations, and 100 to 300 deaths in children less than 5 years old per year in the US. RSV is a common respiratory virus that typically causes mild, cold-like symptoms, usually resolving within a week or two, according to the CDC. However, it can cause severe illness in vulnerable groups such as infants and young children.

A recent study of children with RSV conducted by St. Jude faculty member M. Asunción Mejías, M.D., Ph.D., and colleagues emphasizes that the risk of RSV extends past infancy. The study also highlights age-specific factors associated with severe disease.

In the study, published in Pediatric Allergy and Immunologyon February 16th, researchers identified considerable morbidity associated with RSV in hospitalized infants and children and that the clinical presentation of the illness differed notably depending on the age of the child.

“RSV is the number one cause of hospitalization in infants and young children in the US and all over the world,” Dr. Mejías, pediatric infectious disease expert and lead author of the study, told MHE in an interview. She has been studying RSV for the past 22 years, including investigating factors associated with more severe disease in children.

“We finally have preventive strategies for the young infant population less than 6 months of age, either through maternal vaccination or by directly providing monoclonal antibodies,” Mejías said. She explained that while these RSV prevention strategies will significantly impact the younger infant population, she also emphasized the need to continue developing prevention strategies for older infants, toddlers, and children. Thus, the main goal of the present study was to deeply analyze and describe the clinical presentation of older infants and children hospitalized with RSV.

In this retrospective, single-center study, researchers analyzed electronic health record data from over 5,000 children under five years old hospitalized with RSV during the respiratory seasons of 2012 through 2018 at Nationwide Children’s Hospital in Columbus, OH. The children were stratified by age groups: less than 6 months, 6 to 24 months, and 24 to 59 months (2 to 5 year-olds).

The study showed that nearly half of the children hospitalized with RSV were older than 6 months old. Notably, underlying comorbidities were identified in 37% of the children. Supplemental oxygen was provided to nearly 70% of patients for an average of four days. While more children aged 24 to 59 months received oxygen than infants less than six months, the duration of oxygen therapy was longer in the youngest age group.

The proportion of patients receiving care in the pediatric intensive care unit (PICU) was similar across all three age groups. However, longer PICU stays and more frequent use of mechanical ventilation were observed for infants under 6 months old. The total length of stay was similar among age groups.

The researchers found that the prevalence of underlying comorbidities, such as asthma, significantly increased with age and remained associated with worse disease severity in older children. Detection of concurrent viral infection was found to have a more significant impact during the first two years of life.

“We found that having coinfection with RSV and other virus infections was also a risk factor for severe disease,” Mejías said, acknowledging that their timeframe of data collection was pre-pandemic and that more research is needed to replicate and understand the risk factors of coinfection with specific viruses.

While newer therapies will mainly benefit younger infants, this study highlights the importance of establishing effective prevention and management strategies for children up to age five years old as well.