Vaccination Rates Increase With Electronic Letter Reminder for Influenza Immunization

Interventions of electronic letter-based nudges increase influenza vaccination compared with the usual care for young and middle-aged adults with chronic diseases, according to results of a study (NCT06030739) published in JAMA. In the clinical trial, investigators aimed to determine if digital behavioral nudges delivered by the official electronic letter system could increase influenza vaccine uptake among those aged 18 to 64 years with chronic diseases.^1,2

Electronic letter reminders were most effective for older individuals, those who were unvaccinated in the preceding season, those with cardiovascular disease, and those with diabetes.

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The study was a randomized, open-label implementation trial that included individuals eligible for free-of-charge influenza vaccination due to a chronic condition, including chronic lung disease, cardiovascular disease (excluding hypertension), type 1 or 2 diabetes, congenital or acquired immunodeficiency, impaired breathing due to muscular weakness, and chronic renal or hepatic insufficiency. Investigators included individuals from the Danish health registries using codes from the International Classification of Diseases, 10th Revision. There were 7 arms, with 1 including the standard of care and 6 interventions arms that used different nudging strategies.²

The intervention groups included: a standard letter on the benefits of influenza vaccination without behavioral economic enhancement; the standard letter sent twice instead of once; text added to the standard letter that described the cardiovascular benefits of vaccination; text added to the standard letter on benefits related to respiratory disease; implementation intention prompt added to the standard letter; and text added to the standard letter of potential risks of not receiving influenza vaccination.²

The primary outcome included the number of individuals who received an influenza vaccine up to 3 months, and the secondary outcome measures include time from intervention delivery to influenza vaccination up to 3 months. According to the clinical trial information, other outcomes included number of individuals with laboratory-confirmed influenza, individuals with hospitalization for influenza or pneumonia, individuals hospitalized for any respiratory disease, individuals hospitalized for any cardio-respiratory disease, individuals hospitalized for any cause, and all-cause mortality.²

Investigators included 299,881 individuals in the trial, consisting of a median age of 52 years and 53.2% were female. In the previous season (2022 to 2023) 31.8% received an influenza vaccination. Approximately 85.2% had 1 disease-specific inclusion criterion and 14.8% had 2. Additionally, 20.6% met the cardiovascular disease criterion, 12.2% met the lung disease criterion, 14.5% met the diabetes criterion, and 53% had other chronic conditions, which included cancer, hematologic, neurologic, and autoimmune disease, according to the study authors.¹

During the 2023 to 2024 season, 36.2% received an influenza vaccination. For those in the intervention group, 29.6% received a vaccination compared with 27.9% for the usual care. The group that received the repeated letter had the largest effect observed at 41.8% compared to the standard of care and the cardiovascular letter had an effect of 39.8%. The results were similar in the post hoc analysis, the study authors said.¹

Furthermore, investigators found that the time-to-even outcome was also more likely with the intervention letter compared with the standard of care. Even though the results favored the intervention letter, investigators found that it was most effective for older individuals, those who were unvaccinated in the preceding season, those who had chronic cardiovascular disease, and those who had not qualified due to type 1 or 2 diabetes. The increased vaccination in the study did not result in any substantial differences for the clinical outcomes.¹

REFERENCES

1. Johansen ND, Vaduganathan M, Bhatt AS, et al. Electronic Nudges to Increase Influenza Vaccination in Patients With Chronic Diseases: A Randomized Clinical Trial. JAMA. Published online October 11, 2024. doi:10.1001/jama.2024.21060

2. Nationwide Utilization of Danish Government Electronic Letter System for Increasing InFLUenza Vaccine Uptake Among Adults With Chronic Disease. ClinicalTrials.gov identification: NCT06030739. Updated October 10, 2024. Accessed October 24, 2024. https://clinicaltrials.gov/study/NCT06030739