An interventional study of Routine Influenza Vaccination Recommendation and Repeated AI-Assisted Telephone Intervention in Heart Failure and Influenza Vaccination, sponsored by Heart Health Research Center. Not yet recruiting at 1 site in China. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-19.
Sponsored by Heart Health Research Center · Not applicable, Interventional, and Prevention
Influenza vaccination is an important preventive measure for patients with heart failure (HF), but vaccination uptake remains low in China. Although previous studies have demonstrated the benefits of actively promoting influenza vaccination, scalable strategies to improve vaccination uptake among patients with HF after hospital discharge remain insufficiently evaluated.
The PANDA-BOOST trial is a prospective, pragmatic, open-label, two-stage sequential randomized clinical trial involving participants previously enrolled in the PANDA II trial. The study aims to evaluate whether sequential digital interventions using artificial intelligence (AI)-assisted telephone calls and short message service (SMS) reminders improve influenza vaccination uptake compared with a single routine vaccination recommendation.
After an initial AI-assisted telephone call providing a standardized influenza vaccination recommendation, eligible unvaccinated participants will be randomized in a 1:2 ratio to a routine recommendation group or a sequential digital intervention group. Participants in the sequential intervention group will receive additional AI-assisted telephone calls approximately 14 and 28 days after the initial call. Those who remain unvaccinated and meet eligibility criteria at the third call will undergo a second randomization in a 1:1:1 ratio to no additional SMS, gain-framed SMS, or loss-framed SMS.
The primary outcome is influenza vaccination uptake within two months after the first-stage randomization.
The PANDA-BOOST (Behavioral Optimization of Outreach Strategies Through Technology) trial is a prospective, pragmatic, open-label, two-stage sequential randomized clinical trial designed to evaluate the effectiveness of sequential digital interventions in improving seasonal influenza vaccination uptake among patients previously hospitalized for heart failure.
Study Population Participants will be identified from the population previously enrolled in the PANDA II trial, a multicenter cluster-randomized clinical trial conducted in China. Eligibility for PANDA-BOOST will be determined through an initial AI-assisted telephone assessment. Participants who are successfully contacted, confirmed to be alive, and confirmed not to have received the 2026-2027 seasonal influenza vaccine will be eligible for first-stage randomization. Participants who have already been vaccinated, cannot be successfully contacted, or have an undetermined vaccination status will not undergo first-stage randomization.
First-Stage Randomization
All eligible participants will receive a standardized routine influenza vaccination recommendation during the initial AI-assisted telephone call. Following this assessment, participants will be randomized in a 1:2 ratio to either:
First-stage randomization will use stratified permuted blocks, with stratification based on participants' original randomized assignment in the PANDA II trial.
During the second and third AI-assisted telephone calls, vaccination status will be reassessed. Participants who remain unvaccinated will be asked about their reasons for non-vaccination and will receive another standardized influenza vaccination recommendation. Participants who have already received the seasonal influenza vaccine will not receive further vaccination promotion interventions.
Second-Stage Randomization Participants assigned to the sequential digital intervention group who remain unvaccinated and complete the third AI-assisted telephone assessment will be eligible for second-stage randomization.
Eligible participants will be randomized in a 1:1:1 ratio to one of three groups:
Second-stage randomization will use permuted blocks without stratification. SMS messages will be sent approximately 14 days after second-stage randomization. Participants who receive influenza vaccination after second-stage randomization but before the scheduled SMS intervention will remain in their originally assigned groups for intention-to-treat analysis.
Outcomes and Data Collection The primary outcome is the proportion of participants who receive the 2026-2027 seasonal influenza vaccine within two months after first-stage randomization.
The secondary outcome is the time from first-stage randomization to influenza vaccination.
Exploratory analyses will evaluate the comparative effects of the three second-stage SMS strategies, reasons for non-vaccination, implementation indicators of AI-assisted telephone calls and SMS interventions, all-cause mortality, and influenza-related illness events when reliable data are available.
Vaccination status and vaccination dates will be primarily ascertained through vaccination registry data obtained in collaboration with the Beijing Center for Disease Prevention and Control. Baseline clinical characteristics will be obtained from the existing PANDA II database, supplemented by prospectively collected intervention and follow-up data.
The primary analysis will follow the intention-to-treat principle, comparing vaccination uptake between the first-stage randomized groups. Second-stage comparisons will be conducted as exploratory analyses.
5,803 studies on the registry are indexed under Heart Failure; 1,222 are open to participants now.
This study's planned enrollment of 588 is above the median of 72 across 3,790 interventional studies indexed under Heart Failure.
Browse Heart Failure studies →Heart Health Research Center is the lead sponsor of 7 studies on the registry; 4 are open to participants now.
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Exclusion Criteria:
Eligibility for Second-Stage Randomization:
Among participants assigned to the sequential digital intervention group, those who complete the third AI-assisted telephone assessment and remain unvaccinated against seasonal influenza will be eligible for second-stage randomization. Participants who have been vaccinated, cannot be successfully contacted, or have an undetermined vaccination status at the third assessment will not undergo second-stage randomization.
All participants receive an initial AI-assisted telephone assessment and a standardized influenza vaccination recommendation before first-stage randomization. Participants assigned to the routine recommendation strategy receive no additional study-specific vaccination promotion interventions after randomization.
Behavioral: Routine Influenza Vaccination Recommendation
Participants assigned to the sequential digital intervention strategy are scheduled to receive additional AI-assisted telephone calls approximately 14 and 28 days after the initial call, subject to protocol-defined stopping rules. Participants confirmed to have been vaccinated discontinue further vaccination promotion. Only participants who complete the third telephone assessment and remain unvaccinated undergo second-stage randomization. Those assigned to the no additional SMS strategy receive no study-specific SMS reminder. Participants who do not undergo second-stage randomization remain in the first-stage intention-to-treat population.
Behavioral: Repeated AI-Assisted Telephone Intervention
Participants assigned to the sequential digital intervention strategy are scheduled to receive additional AI-assisted telephone calls approximately 14 and 28 days after the initial call, subject to protocol-defined stopping rules. Participants confirmed to have been vaccinated discontinue further vaccination promotion. Only participants who complete the third telephone assessment and remain unvaccinated undergo second-stage randomization. Those assigned to the gain-framed SMS strategy receive one gain-framed vaccination reminder approximately 14 days after second-stage randomization. Participants who do not undergo second-stage randomization remain in the first-stage intention-to-treat population.
Behavioral: Repeated AI-Assisted Telephone Intervention · Behavioral: Gain-Framed SMS Reminder
Participants assigned to the sequential digital intervention strategy are scheduled to receive additional AI-assisted telephone calls approximately 14 and 28 days after the initial call, subject to protocol-defined stopping rules. Participants confirmed to have been vaccinated discontinue further vaccination promotion. Only participants who complete the third telephone assessment and remain unvaccinated undergo second-stage randomization. Those assigned to the loss-framed SMS strategy receive one loss-framed vaccination reminder approximately 14 days after second-stage randomization. Participants who do not undergo second-stage randomization remain in the first-stage intention-to-treat population.
Behavioral: Repeated AI-Assisted Telephone Intervention · Behavioral: Loss-Framed SMS Reminder
A single standardized influenza vaccination recommendation is provided during the initial AI-assisted telephone call before first-stage randomization. The call also assesses contact status, survival status, and current-season vaccination status.
Participants assigned to the sequential digital intervention strategy receive additional AI-assisted telephone calls approximately 14 and 28 days after the initial call. Vaccination status is reassessed, and unvaccinated participants are asked about reasons for non-vaccination and receive a repeated vaccination recommendation. Further intervention is discontinued for participants confirmed to have been vaccinated.
One gain-framed SMS message emphasizing the potential health protection associated with influenza vaccination is sent approximately 14 days after second-stage randomization to participants assigned to this strategy.
One loss-framed SMS message emphasizing the potential loss of protection and continued influenza-related health risks associated with non-vaccination is sent approximately 14 days after second-stage randomization to participants assigned to this strategy.
Influenza Vaccination Uptake
The proportion of participants who receive the 2026-2027 seasonal influenza vaccine within two calendar months after first-stage randomization. Vaccination status will be determined primarily using vaccination registry data from the Beijing Center for Disease Prevention and Control. Participants with a qualifying vaccination record within the assessment window will be classified as vaccinated. Participants with adequate registry coverage but no qualifying record will be classified as unvaccinated. Outcomes that cannot be reliably ascertained will be recorded as indeterminate.
Time frame: From first-stage randomization to 2 months after randomization
From first-stage randomization to 2 months after randomization
Time in days from first-stage randomization to receipt of the 2026-2027 seasonal influenza vaccine, based on the recorded vaccination date. Participants who do not receive influenza vaccination within the two-month assessment window will be right-censored at the end of their individual assessment window. Time-to-event analyses will be used to compare the first-stage randomized groups.
Time frame: From first-stage randomization to 2 months after randomization
Influenza Vaccination Uptake Following Second-Stage Randomization
The proportion of participants receiving the 2026-2027 seasonal influenza vaccine across the three second-stage randomized groups: no additional SMS, gain-framed SMS, and loss-framed SMS. Comparisons will be exploratory and follow the intention-to-treat principle.
Time frame: From 14 to 28 days after second-stage randomization
From 14 to 28 days after second-stage randomization
The proportion of scheduled AI-assisted telephone calls successfully completed among participants eligible for each call, assessed separately by telephone round.
Time frame: During the intervention period, up to 4 weeks after first-stage randomization
Reasons for Non-Vaccination
The distribution of predefined reasons for not receiving influenza vaccination among unvaccinated participants assessed during the second and third AI-assisted telephone calls. Multiple reasons may be recorded for each participant.
Time frame: At approximately 14 and 28 days after first-stage randomization
All-Cause Mortality
The proportion of participants who die from any cause within two calendar months after first-stage randomization, ascertained using available reliable data sources.
Time frame: From first-stage randomization to 2 months after randomization
Influenza-Related Illness Events
The occurrence of influenza-related illness events during follow-up, assessed using available authorized disease surveillance or registry data. Event definitions will be prespecified based on the available data.
Time frame: From first-stage randomization to 2 months after randomization
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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Heart Health Research Center