Sanofi has officially ended its Phase III trial for a respiratory syncytial virus (RSV) vaccine targeting toddlers—citing futility as the reason for halting development. In this episode of The Biotech Brief, we unpack what happened and why it matters. From the biology of RSV and the unique challenges of vaccinating toddlers, to the competitive market landscape and strategic risks for pharma companies, we take you behind the headlines.   We explore how the program could’ve been salvaged through trial redesign, alternative regulatory strategies in lower-bar jurisdictions, or refined target populations—and why Sanofi may have opted out anyway. We also consider the wider implications for pediatric vaccine development, especially in an era of rising vaccine skepticism and shifting policy dynamics.   If you’re a biotech innovator, investor, or strategist, this episode offers insights into what it really takes to bring a pediatric vaccine to market—and what we can learn when a promising candidate falls short.