Communication Intervention to Improve Influenza Vaccination Rates Among Elderly in Can Tho (CIVECT)

Effectiveness of Community-Based Communication Interventions to Improve Influenza Vaccination Rates Among the Elderly in Vietnam: A Cluster Randomized Controlled Trial

This study evaluates the effectiveness of a multi-component community-based communication intervention to increase influenza vaccination rates among adults aged above 65 years in Can Tho City, Vietnam. Using a cluster randomised controlled trial design with stratified lottery randomisation, four study sites were selected from eight sites surveyed in a prior study: O Mon Ward and Truong Thanh Commune (intervention); Phuoc Thoi Ward and Truong Xuan Commune (control). The intervention includes community health education sessions, healthcare worker training, household visits, health communication banners, and Zalo-based vaccination reminders, delivered over 12 months (September 2025 to September 2026). Effectiveness is assessed by comparing pre- and post-intervention outcomes using Difference-in-Differences (DID) analysis.

Study Overview

• Status: Active, not recruiting
• Conditions: Influenza; Health Communication; Vaccination Coverage
• Intervention / Treatment: Behavioral: Multi-component Health Communication Package

Detailed Description

This study employs a cluster randomised controlled trial (cluster RCT) design with a repeated cross-sectional approach. The unit of randomisation is the cluster (ward or commune).

RANDOMISATION:

From eight study sites surveyed in Objective 1 (four urban wards and four rural communes in Can Tho City), four sites were selected by stratified lottery randomisation. Within each stratum (urban and rural), one site was randomly assigned to the intervention group and one to the control group by lottery draw without investigator discretion:

• Intervention: O Mon Ward (urban) and Truong Thanh Commune (rural)
• Control: Phuoc Thoi Ward (urban) and Truong Xuan Commune (rural)

PARTICIPANTS:

All eligible permanent residents aged above 65 years at each study site were invited to participate. Data are collected at two independent cross-sectional time points:

• T0: Baseline survey, August 2025 (n=952)
• T1: Follow-up survey, September 2026 (n=approximately 1,200) Participants at T0 and T1 are not necessarily the same individuals; the design captures population-level changes within randomised clusters.

INTERVENTION (12 months: September 2025 to September 2026):

The 12-month duration encompasses both active implementation and the time required for knowledge, attitude, and behaviour change.

Phase 1 (September 2025, intensive activities):

• Two community health education sessions per intervention site for adults aged >65 years and one cohabiting family member, with distribution of printed educational leaflets on influenza disease and vaccination. Attendance: O Mon Ward: Session 1 = 60 older adults + 40 family members, Session 2 = 57 older adults + 35 family members; Truong Thanh Commune: Session 1 = 60 + 38, Session 2 = 50 + 30.
• One capacity-building workshop per site for healthcare workers and community health volunteers in vaccination counselling (O Mon Ward: n=30; Truong Thanh Commune: n=20).
• Thirty household visits per site by trained community health volunteers to reinforce vaccination counselling.

Phase 2 (September 2025 to September 2026, ongoing):

• Health communication banners displayed at health stations and community information centres throughout the intervention period.
• Healthcare worker vaccination counselling integrated into all routine clinical contacts at intervention site health stations.
• Zalo-based digital communication: weekly educational content and personalised vaccination reminders (December 2025 to January 2026, coinciding with peak influenza season in southern Vietnam).

CONTROL GROUP:

Received routine primary healthcare only, with no additional study-related activities.

ANALYSIS:

Effectiveness is measured using Difference-in-Differences (DID) regression, comparing changes between T0 and T1 across intervention and control clusters. Models use multivariable logistic regression (binary outcomes) and linear regression (continuous outcomes), adjusted for sociodemographic covariates. Intraclass correlation coefficients (ICC) were estimated for all outcomes and found to be negligible (ICC < 0.01), confirming the appropriateness of individual-level DID analysis.

• Study Type: Interventional
• Enrollment (Estimated): 1200
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Vietnam
  • Can Tho City
    • Can Tho, Can Tho City, Vietnam, 900000
      • Can Tho University of Medicine and Pharmacy

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Residents living in selected wards/communes in Can Tho City for at least 6 months.
• Aged above 65 years.
• Mentally and physically capable of participating in interviews and receiving communication interventions.
• Agree to participate in the study and provide informed consent.

Exclusion Criteria:

• Individuals with severe cognitive impairment or dementia.
• Individuals with contraindications to influenza vaccination.
• Planning to move out of the study area during the 12-month follow-up period.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
No Intervention: Routine Immunization Information; Participants in this arm receive standard care and routine immunization information provided by the local health station without the additional communication package.
Experimental: Multi-component Health Communication; Adults aged >65 years in 2 intervention clusters (O Mon Ward and Truong Thanh Commune) receive a multi-component package: Phase 1 (Sep 2025): (1) Two community health education sessions/ site for older adults and one family member, with influenza leaflets. (2) One HCW capacity-building workshop/site (O Mon: n=30; Truong Thanh: n=20). (3) Thirty household visits/site by community health volunteers. Phase 2 (Sep 2025-Sep 2026): (4) Health communication banners at health stations and community centres. (5) HCW point-of-care vaccination counselling at all clinical contacts. (6) Zalo-based weekly reminders and educational content (Dec 2025-Jan 2026).	Behavioral: Multi-component Health Communication Package; A 12-month cluster-level communication intervention (Sep 2025-Sep 2026) delivered in two phases to all adults aged >65 years in intervention clusters: Phase 1 (Sep 2025): (1) Two community health education sessions/site with influenza leaflets for older adults and family members; (2) HCW capacity-building workshop/site (O Mon: n=30; Truong Thanh: n=20); (3) Thirty household visits/site by community health volunteers. Phase 2 (ongoing): (4) Health communication banners at health stations and community centres; (5) HCW point-of-care vaccination counselling at all clinical contacts; (6) Zalo-based weekly educational content and vaccination reminders (Dec 2025-Jan 2026).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Influenza vaccination uptake in the preceding 12 months	Proportion of participants who received influenza vaccination in the 12 months prior to survey, assessed by self-report. Baseline assessed August 2025; follow-up assessed September 2026. Intervention effect estimated using Difference-in- Differences (DID) regression comparing change between intervention and control clusters.	Up to 12 months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Influenza vaccination in calendar year 2025	Proportion vaccinated against influenza during calendar year 2025, assessed by self-report at follow-up (September 2026).	Up to 12 months
Influenza vaccination intention	Proportion intending to receive influenza vaccination in the next 12 months, assessed by self-report at baseline (August 2025) and follow-up (September 2026).	Baseline and up to 12 months
Healthcare worker vaccination counselling	Proportion who received influenza vaccination counselling from a healthcare worker or community health volunteer in the preceding 12 months, assessed by self-report at baseline (August 2025) and follow-up (September 2026).	Baseline and up to 12 months
Influenza knowledge score	Total knowledge score (0-6) on influenza disease aetiology, transmission, complications, and vaccine characteristics. Higher scores indicate greater knowledge. Assessed at baseline (August 2025) and follow-up (September 2026). Analysed using linear regression DID.	Baseline and up to 12 months
Vaccine hesitancy score (WHO-SAGE Vaccine Hesitancy Scale)	Vaccine hesitancy measured using the WHO-SAGE Vaccine Hesitancy Scale (Vietnamese-adapted version). Higher scores indicate greater hesitancy. Assessed at baseline (August 2025) and follow-up (September 2026). Analysed using linear regression DID.	Baseline and up to 12 months
Willingness to pay for influenza vaccination	Proportion willing to pay out-of-pocket costs for influenza vaccination, assessed by self-report binary question at baseline (August 2025) and follow-up (September 2026).	Baseline and up to 12 months

Collaborators and Investigators

• Sponsor: Can Tho University of Medicine and Pharmacy
• Collaborators: National Institute of Hygiene and Epidemiology, Vietnam

Study record dates

Study Major Dates

• Study Start (Actual): September 1, 2025
• Primary Completion (Estimated): September 1, 2026
• Study Completion (Estimated): December 1, 2026

Study Registration Dates

• First Submitted: March 27, 2026
• First Submitted That Met QC Criteria: March 27, 2026
• First Posted (Actual): April 2, 2026

Study Record Updates

• Last Update Posted (Actual): July 6, 2026
• Last Update Submitted That Met QC Criteria: June 30, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: Elderly; Vietnam; Influenza Vaccines; Health Communication; Community-based Intervention; Vaccination Coverage
• Additional Relevant MeSH Terms: Respiratory Tract Infections; Infections; Orthomyxoviridae Infections; RNA Virus Infections; Virus Diseases; Respiratory Tract Diseases; Influenza, Human
• Other Study ID Numbers: NIHE IRB - 40/2025

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data (IPD) will not be shared with other researchers to ensure the privacy and confidentiality of the study participants, in accordance with local ethical guidelines and institutional policies. Only aggregated results will be made available through publications.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No