LAUSR

OBJECTIVE Presumptive formats to initiate childhood vaccine discussions (eg, "Well, we have to do some shots") have been associated with increased vaccine acceptance after one visit compared to participatory formats (eg, "How do you feel about vaccines?"). We characterize discussion format patterns over time and the impact of their repeated use on vaccine acceptance. METHODS We conducted a longitudinal prospective cohort study of children of vaccine-hesitant parents enrolled in a Seattle-based integrated health system. After the child's 2-, 4-, and 6-month visits, parents reported the format their child's provider used to begin the vaccine discussion (presumptive, participatory, or other). Our outcome was the percentage of days underimmunized of the child at 8 months old for 6 recommended vaccines. We used linear regression and generalized estimating equations to test the association of discussion format and immunization status. RESULTS We enrolled 73 parent-child dyads and obtained data from 82%, 73%, and 53% after the 2-, 4-, and 6-month visits, respectively. Overall, 65% of parents received presumptive formats at ≥1 visit and 42% received participatory formats at ≥1 visit. Parental receipt of presumptive formats at 1 and ≥2 visits (vs no receipt) was associated with significantly less underimmunization of the child, while receipt of participatory formats at ≥2 visits was associated with significantly more underimmunization. Visit-specific use of participatory (vs presumptive) formats was associated with a child being 10.1% (95% confidence interval, 0.3, 19.8; P = .04) more days underimmunized (amounting to, on average, 98 more days underimmunized for all 6 vaccines combined). CONCLUSIONS Presumptive (vs participatory) discussion formats are associated with increased immunization.