Drivers of decision-making for future adult vaccines: a best–worst scaling among community members and health care workers in Zambia

Background: Several new vaccines for adults may soon become available, but low- and middle-income countries (LMICs) have limited experience with adult vaccination programs beyond COVID-19. Understanding the factors that influence vaccination decisions among community members and healthcare workers (HCWs) in such settings will be critical for optimizing uptake and rollout strategies. Methods: We conducted a Best-Worst Scaling (BWS) exercise to determine which vaccination factors (n = 22) most influenced adult community members and HCWs in Lusaka, Zambia, for newly introduced vaccines. Vaccination factors included disease characteristics, vaccine characteristics, vaccine-related concerns, vaccine delivery features, social norms, and external motivators. Mean preference weights (MPWs), indicating relative importance, were calculated using hierarchical Bayes, and latent class multinomial logit analyses (LCA) were used to identify distinct preference groups. Results: Of 472 participants (median age 30.0 years, 53.8% female, 9.6 % HIV-positive), 381 (76.4 %) were community members, and 91 (19.3 %) were HCWs. Disease characteristics (specific disease, infection likelihood, severity) and vaccine characteristics (efficacy, protection duration) were the most important factors influencing vaccine decision-making. LCA identified five community member and two HCW groups– all prioritized the specific disease targeted by the vaccine. Community groups included “Personal Health-Focused” (31.0 %, prioritizing disease severity and future vaccine-related health problems), “Disease Protection and Social Awareness” (22.8 %;prioritizing vaccine protection duration, broader social norms), “Incentive Motivated” (18.9 %; prioritizing financial incentives), “Vaccine Cautious” (15.5 %;prioritizing vaccine origin, safety concerns), and “Mandate Motivated” (11.8 %;prioritizing vaccination requirements). HCW groups were, “Disease and Efficacy Driven” (62.6 %;prioritizing vaccine effectiveness, disease severity, side effects) and “Pragmatic Minded “ (37.4 %;prioritizing number of doses, protection duration, pregnancy safety). Conclusions: While disease-specific factors commonly shaped vaccine preferences, heterogeneity among community members and HCWs highlights the need for differentiated delivery and communication strategies that incorporate group-specific motivations and utilize trusted sources to optimize uptake of future adult vaccines in Zambia and other LMICs.