McFarland EJ, et al. - Live respiratory syncytial virus (RSV) candidate vaccine LIDΔM2-2 is attenuated by deletion of the RSV RNA regulatory protein M2-2, resulting in upregulated viral gene transcription and antigen expression but reduced RNA replication. Among RSV-seronegative children ages 6–24 months receiving a single intranasal dose of 10⁵ plaque forming units (PFU) of LIDΔM2-2, researchers assessed RSV serum antibodies, vaccine infectivity, and reactogenicity. Findings revealed LIDΔM2-2 to have excellent infectivity and immunogenicity.