Digital reminders and donor return: A randomised evaluation of short message service , WhatsApp and telephone calls in a Nigerian tertiary hospital

Background Maintaining an adequate and safe blood supply is a major challenge in low‐ and middle‐income countries, where donor lapse and low voluntary donation rates hinder sustainability. Mobile communication technologies such as short message service (SMS), WhatsApp and telephone calls offer scalable approaches to donor outreach, but their comparative effectiveness in re‐engaging lapsed and inactive donors in sub‐Saharan Africa remains insufficiently studied. Objectives This study assessed the effectiveness of these communication tools in re‐engaging lapsed (no donation within 12 months despite donation within the prior 24 months) and inactive donors (no donation for >24 months) at Lagos University Teaching Hospital (LUTH), using re‐donation within 30 days as the primary outcome. Study Design and Methods A stratified, randomised interventional study with computer‐generated allocation, stratified by age, sex and donor status, was conducted among lapsed and inactive voluntary blood donors at LUTH. Donors were allocated to one of four groups: SMS, WhatsApp message, telephone call or no‐intervention control, and followed for 30 days. Secondary outcomes included message delivery and donor response. Sociodemographic variables and self‐reported barriers to return were also assessed. Results Of 3014 donors identified, 2809 met eligibility criteria and were randomised. Among 2107 donors who received attempted contact, 1546 (73.4%) were successfully reached. SMS achieved the highest delivery rate (95.4%), followed by telephone calls (63.8%) and WhatsApp messages (60.8%). Positive responses were recorded in 429 (27.7%) donors, with 421 (98.1%) arising from telephone outreach. SMS generated eight positive responses (1.9%), and WhatsApp produced none. Only one donor, belonging to the telephone group, returned to donate during follow‐up, yielding an overall re‐donation rate of 0.04%. Reported barriers included time constraints, occupational demands and long distance to the donation centre. Conclusion Telephone calls elicited the strongest immediate engagement, but single‐contact reminders, regardless of modality, were insufficient to generate meaningful short‐term donor return. Effective donor retention strategies in Nigeria will require multi‐contact outreach, personalised communication and interventions addressing structural barriers such as scheduling and distance.