The COVID-19 pandemic resulted in substantially lower uptake of childhood vaccinations in the U.S. As vaccination rates struggle to rebound, childhood vaccine hesitancy continues to grow. Addressing vaccine disinformation and increasing catch-up vaccination is an urgent public health priority. The purpose of this study was to evaluate the effectiveness of "Jenny's First Sleepover," a darkly humorous satirical book about childhood vaccinations, to influence attitudes of vaccine hesitant parents. This study implemented a randomized pretest - posttest experimental design using a web-based survey with one intervention and one control. "Jenny's First Sleepover" improved attitudes toward vaccination among vaccine hesitant parents. Negative emotions were an important mediator of attitudes toward vaccinations. Findings identify mechanisms that increase effectiveness of satirical approaches, including the presentation of novel information about serious vaccine-preventable diseases with a dark narrative twist. Health communicators may consider a darkly humorous satirical approach to improve attitudes toward childhood vaccination among vaccine hesitant parents.