Three-Year Follow-Up of the PACI Randomized Controlled Trial (PACI-ON): Effects of Early Intervention for Atopic Dermatitis on Atopic March

Background: The Prevention of Allergy via Cutaneous Intervention (PACI) randomized controlled trial (RCT) demonstrated that early enhanced topical corticosteroid (TCS) therapy modestly reduced food allergy (FA) at 28 weeks of age. The present prospective follow-up study (PACI-ON) evaluated whether these effects persisted to age 3 years. Methods: Participants were randomized in infancy to early enhanced (proactive) or early conventional (reactive) TCS treatment (1:1) for atopic dermatitis (AD) until 28 weeks. A total of 590 (91%) children who completed the PACI RCT were followed to age 3 years. During follow-up, no protocolized interventions were given; all participants received usual care. Main outcomes included physician-diagnosed FA, AD severity (EASI, POEM), sensitization profiles, allergic comorbidities, and growth parameters as safety outcomes. Results: At age 3 years, the prevalence of any FA remained lower in the early enhanced group than in the conventional group (47.4% vs. 58.8%, p = 0.006), mainly driven by a reduced prevalence of raw egg allergy (30.4% vs. 40.5%, p = 0.013). No between-group differences were observed for wheeze, asthma, or rhinitis. Japanese cedar sensitization at age 2 was lower in the enhanced group (6.1% vs. 12.2%, p = 0.02 6) but not at age 3. AD control and quality of life were well maintained and similar across groups, with > 90% achieving mild or less disease. Early growth suppression at 1 year resolved by age 3. Conclusion: Early enhanced AD intervention was associated with a sustained modest reduction in its planned primary follow-up outcome of FA and safety (growth) up to age 3. Although most differences were small and may reflect early diagnosis and good overall management in both groups, the findings support early AD treatment as a potential strategy to modify allergic disease trajectories.