Two new studies, one focused on children with complex medical needs and the other on adults, shed fresh light on how widespread and serious respiratory syncytial virus (RSV) infections can be and the unique susceptibility infants born with Down syndrome may have.

Children with Complex Medical Conditions Face Highest RSV Hospitalization Risk

A study published in JAMA Network Open tracked over 430,000 children in British Columbia, including more than 25,000 with at least one chronic medical condition (CMC). The findings are sobering: children with CMCs—especially those involving multiple systems like the respiratory, cardiovascular, or gastrointestinal systems—had hospitalization rates for RSV that were more than three times higher than those without such conditions.

The risk was particularly elevated in children with Down syndrome or who were born prematurely. By their second RSV season, these children were hospitalized at rates five times higher than the general pediatric population in their first season.

The University of Minnesota researchers concluded that these results support consideration of long-acting monoclonal antibody prophylaxis beyond the first RSV season for children with high-risk conditions. “Hospitalization rates in the second RSV season among children with CMCs were similar to rates among all children in their first season,” the authors wrote, adding that a universal immunization strategy may be warranted for vulnerable groups.

Most Adults Have Been Exposed to RSV, Even Without Knowing It

The second study, published in the International Journal of Infectious Diseases, focused on adults aged 27 to 99 using blood samples from a Mayo Clinic repository. Researchers found that 84% of adults had antibodies to RSV, indicating prior exposure—even among those without any recent symptoms.

Among adults recently vaccinated against RSV or with documented infection, the rate of antibody presence was even higher—around 96% or more. Interestingly, men showed significantly higher antibody titers than women, and a seasonal rise in titers suggested ongoing silent spread of the virus.

The study also emphasized that RSV exposure is not only widespread but may go unnoticed in healthy adults, reinforcing the case for increased surveillance and vaccination among older or immunocompromised populations.

Key Takeaways

• Children with multisystem CMCs are especially vulnerable to RSV-related hospitalization, with risks extending into their second RSV season.
• Infants with Down syndrome or born prematurely face the highest risks.
• Long-acting RSV antibody treatment may be needed for a second season in high-risk children.
• More than 8 in 10 adults have already encountered RSV—often without realizing it.
• Men tend to have higher RSV antibody levels, and immunity can wane over time.

These studies, spotlighted by the University of Minnesota, offer critical insight into the long-term management and prevention of RSV in both pediatric and adult populations. As vaccine options expand, these findings could shape future public health recommendations.