Examining the Feasibility, Acceptability, and Preliminary Efficacy of a Health App for Postacute Pandemic Years in Managing Physical and Psychological Distress Symptoms: Pilot Quasi-Experimental Study

Background Physical and psychological distress symptoms can adversely affect daily functioning and quality of life, highlighting the need for accessible self-management support. Although mobile health (mHealth) interventions show promise in supporting physical symptom management, evidence regarding their feasibility and potential effects on psychological distress remains limited. Objective This pilot study aimed to evaluate the feasibility, acceptability, and preliminary efficacy of the health app for postacute pandemic years (HAPPY) for managing physical and psychological distress symptoms. Methods A 2-arm, single-blind, quasi-experimental trial was conducted from July 2023 to January 2024. Thirty-eight participants experiencing distress symptoms related to COVID-19 were assigned to the experimental group or a waitlist control group. The experimental group received a 24-week mHealth intervention through the HAPPY app, which included an 8-week supervised phase with weekly face-to-face sessions and a 16-week self-management phase. The control group received no active treatment. Feasibility was assessed through recruitment, adherence, and adverse event monitoring, whereas preliminary efficacy was evaluated at 8 weeks (T1) and 24 weeks (T2) and compared with baseline (T0) using quantitative measures of distress, fatigue, sleep quality, pain, emotional regulation, and posttraumatic stress disorder (PTSD). Results The study demonstrated the feasibility of the HAPPY app, with a recruitment rate of 88.37% (38/43), a dropout rate of 10.5% (4/38), and an adherence rate of 93.33% (14/15) for the supervised sessions. No adverse events were reported. Significant within-group improvements were observed for distress (Kessler Psychological Distress Scale [K10]; P<.001), fatigue (Brief Fatigue Inventory–Chinese [BFI-C]; P<.001), sleep quality (Chinese Pittsburgh Sleep Quality Index [CPSQI]; P=.009), and PTSD symptoms (Chinese Impact of Event Scale–Revised [CIES-R]; P=.02). However, between-group differences were limited. Conclusions The study demonstrated the HAPPY app’s feasibility, acceptability, and potential efficacy for managing physical and psychological distress symptoms. High recruitment, retention, and adherence rates, along with measurable improvements in distress, fatigue, sleep quality, and pain, suggest the app’s promise as a scalable intervention. Trial Registration ClinicalTrials.gov NCT05459896; https://clinicaltrials.gov/study/NCT05459896