This episode of PEM Currents: The Pediatric Emergency Medicine Podcast focuses on the approach to unvaccinated or undervaccinated children aged 3–36 months presenting to the ED with fever. Host Brad Sobolewski reviews differences in immune response, risk for serious and invasive bacterial infections, and outlines evaluation strategies including labs, imaging, and empiric antibiotics. He highlights data showing increased interventions in this population and calls for local guideline development. The episode emphasizes thoughtful, individualized care in the context of rising vaccine hesitancy and declining immunization rates.