ABSTRACT In the United States (US), parents’ decision to delay or refuse vaccines for their children has resulted in pockets of under-vaccination as well as recurring outbreaks of vaccine-preventable diseases. To increase childhood vaccinations and stem recurring outbreaks, we need effective interventions that build parents’ confidence in vaccines and reduce their vaccine hesitancy. The first recommended routine vaccination for children is due at birth. Yet, many parents lack timely or evidence-based information on childhood vaccinations prior to their child’s birth. Hence, we propose to evaluate ADEPT - an adaptive intervention that is implemented in prenatal care settings to proactively connect parents with evidence-based childhood vaccination information before their child’s birth. The core component of ADEPT includes prenatal provider trainings and a recommendation to pregnant women in their early third trimester (28-32 weeks) encouraging childhood vaccinations after the child is born. Those pregnant women who remain vaccine-hesitant despite the provider recommendation will receive adaptive intervention components, which include evidence-based educational materials on childhood vaccinations and phone consultations with a vaccine navigator to discuss any residual concerns. Within the framework of a type 1 effectiveness-implementation hybrid study design, we will use a cluster-randomized trial to determine the effectiveness of ADEPT compared to standard of care and a nested explanatory sequential mixed methods study to identify implementation outcomes such as intervention acceptability, feasibility, and fidelity. The proposed study will target pregnant women who are expecting their first child, since research suggests that many of them rely on vaccination information from the internet or other non-healthcare sources, making them susceptible to misinformation and vaccine hesitancy. In the proposed study, ADEPT will be implemented and evaluated in diverse prenatal care practices in North Carolina. In partnership with an external stakeholder advisory team, we will develop a blueprint for future implementation and evaluation of ADEPT in diverse prenatal care settings across the US. Our proposal is innovative as it creates a new paradigm for childhood vaccination education during prenatal care, and implements a novel adaptive intervention (ADEPT) that is tailored to the hesitancy status and concerns of pregnant women. We hypothesize that implementation of ADEPT in prenatal care settings will proactively reduce vaccine hesitancy among pregnant women who are expecting their first child, and increase timely vaccinations for their child post- birth. Our proposal is significant because it aligns with CDC’s Vaccinate with Confidence priorities for empowering families and stopping vaccine myths. Our proposal also supports the Healthy People 2030 goals to reduce the proportion of un- or under-immunized children in the US. The successful completion of propos...