JMIR Publications

ABSTRACT

Background:

The coverage of influenza vaccination among elderly in Norway is insufficient, especially in some immigrant groups. To improve public health, there is a need for an intervention that can increase influenza vaccination coverage. Further, interventions tailored to reduce potential barriers among immigrants can reduce health inequities.

Objective:

InfluSMS aims to determine if SMS nudging increases vaccination coverage among those aged 65 or older (i) in Norway’s general population; (ii) among immigrants born in Poland; (iii) among immigrants born in Ukraine; and to evaluate the impact of SMS nudging in Norwegian versus in the official language of the native country of immigrants born in Poland or Ukraine.

Methods:

InfluSMS is a pragmatic randomized controlled trial conducted among people aged 65 or older residing in Norway. Influenza vaccination coverage is the main outcome, measured in control and intervention arms for each of the three populations listed above. In all three populations, the control arm is standard care, i.e., no individual reminder for influenza vaccination. All populations have an intervention arm that will receive an SMS nudge in the Norwegian language. In addition, the Polish and Ukrainian immigrant populations include a second intervention arm that will receive an SMS nudge in Polish or Ukrainian, respectively. In the general population, at least 23,485 individuals are randomized to the SMS intervention arm while the rest of the population constitute the control arm. In each of the two immigrant populations, we randomize all eligible individuals 1:1:1 into the three arms. The intervention will take place at the start of the 2025/2026 influenza season. All eligible individuals will be passively followed up through the National Immunisation Registry SYSVAK, from which individual influenza vaccination status three months after the SMS nudge will be collected. Coverage rates between arms within each population, and effect sizes between the populations will be compared. The cost-effectiveness of SMS nudging will also be assessed.

Results:

Inclusion of participants will start in the third quarter of 2025, and the registry data will be available in the first quarter of 2026. Coverage rates of each strategy and coverage differences between strategies will be presented.

Conclusions:

SMS nudging is a scalable, inexpensive and non-intrusive intervention that could be integrated into the national influenza vaccination program if the trial shows it effectively increases influenza vaccination coverage among the elderly. Further, the trial will establish whether language is a barrier for influenza vaccination uptake among recent immigrant groups that have low influenza vaccination coverage, and to what extent this potential barrier can be diminished by SMS nudging in the official language of their native country. Clinical Trial: Clinicaltrials.gov (NCT06486766)