Speaker
Description
Respiratory Syncytial Virus (RSV) is the leading cause of infant hospitalizations. During the SARS-CoV-2 pandemic, non-pharmaceutical measures (NPIs) such as masking and physical distancing resulted in very low circulating levels of RSV. When measures were relaxed, RSV-related hospitalizations surged among infants in many jurisdictions, far exceeding usual seasonal levels. Many have attributed this surge to the accumulation of susceptible infants during NPIs. However, this does not explain how total infections can decrease while pediatric intensive care hospitalizations increase, as was reported in Europe during the 2020-2021 season. We present an epidemiological model focused on placentally transferred maternal antibodies which protect infants from severe infections. During the pandemic, the reduction in general RSV circulation meant that fewer infants were born with maternal antibodies. Additionally, the time to first infection increased, leading to waning of maternal antibody protection before first infection. We show that decreasing RSV circulation among adults leads to an increase in the number of first-time infections without protective maternal antibodies. Temporal simulations show that infants were least protected from severe infection soon after pandemic-era public health policies were relaxed. We conclude that maternal antibodies play a major explanatory role in the dynamics of RSV-related hospitalizations. We further predict that general-population vaccination campaigns are likely to lead to an increase in higher-risk infections among infants. Importantly, treatments that are currently being widely implemented, such as maternal vaccination during pregnancy and monoclonal antibody treatment to infants, can effectively protect infants against the potential adverse effects of reduced RSV circulation.
