Walsh EE, et al. - In view of the possible influence of maternally derived serum antibody and viral load on disease severity in primary Respiratory Syncytial Virus (RSV) infection, researchers sought for correlation of various serum antibody concentrations and viral load with disease severity (as part of the AsPIRES study of RSV pathogenesis). No relationship between measures of serum antibody and severity was revealed in the univariate analysis. However, a multivariate model, adjusting for age at the time of infection, demonstrated a marked 0.56 decrease in severity score for each 2-fold increase in antibody concentration to RSV F protein. The concept of maternal immunization with an RSV vaccine during pregnancy was supported as a strategy for reducing the burden of RSV infection in full-term healthy infants exposed to RSV during their first winter.