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Electronic nudges sent to patients failed to increase influenza vaccine uptake in one randomized clinical trial, while another trial found that slight increases in vaccination rates from letters emailed to patients failed to impact clinical outcomes.

Neither portal nor text messages to remind patients to get an influenza vaccination were effective at a population level at improving vaccination uptake, Peter Szilagyi, MD, MPH, of the UCLA Mattel Children's Hospital at the University of California in Los Angeles, and colleagues reported in . Among patients who received care from 79 primary care practices in a large healthcare system, flu shot rates remained at approximately 47% whether patients received portal messages, text messages, or no reminders at all.

And in an analysis of the Danish NUDGE-FLU trial, an about 1% boost in influenza vaccination associated with email letters encouraging patients to get vaccinated did not translate into improvements in cardiovascular, respiratory, or other clinical endpoints, Niklas Johansen, MD, of the Copenhagen University Hospital-Harlev and Gentofte in Denmark, and colleagues wrote in the .

Potential Advantage to Text Messages

Szilagyi and investigators found that patient portal messages sent monthly or before scheduled visits did not increase influenza vaccination rates.

However, preappointment reminders sent 24 to 48 hours before a scheduled primary care appointment, by either text or patient portal, had a small positive effect on vaccine uptake (adjusted risk ratio [aRR] 1.04, 95% CI 1.01-1.06, P=0.01) in a subgroup of patients who were unvaccinated but had at least one primary care appointment. This effect seemed to be driven by text preappointment reminders, which were associated with an absolute increase in vaccination rates of 1.6-1.8% (aRR 1.07, P=0.002), whereas the portal preappointment reminders had no significant impact.

"We suspect there are several reasons why text, but not portal, preappointment reminders were effective," Szilagyi and colleagues wrote. "Portal messages require patients to open the portal and find and then read the message, whereas text messages appear instantly and might appear more urgent or important."

Given the results of their study, the authors concluded that "text message preappointment reminders can be effective for patients with scheduled appointments," but health systems might opt for more intensive interventions instead, "such as improving access to vaccinations (e.g., Saturday or after-hours clinics) or communication training for clinicians to address vaccine hesitancy."

The trial included patients 6 months of age or older in the UCLA Health System with either one or two visits to a primary care provider within the past year or who were enrolled in managed care within the system. The trial included 262,085 patients, 9% of whom where children. Mean age was 45 years: females accounted for 57% of participants, 53% were white, 12% were Hispanic or Latino, and 10% were Asian. Most (83.5%) had private health insurance, and 14.9% received Medicare. About 65% had received an influenza vaccination within 2 years.

Patients were randomized equally to receive standard of care, influenza vaccine portal reminders, or vaccine text reminders. Those randomized to the portal reminder group were further randomized to receive fixed or responsive monthly portal reminders, with or without preappointment reminders. Those randomized to the text reminder group received fixed monthly reminders and were further randomized to receive preappointment reminders or no preappointment reminders.

The primary outcome was influenza vaccination, including vaccination at pharmacies and other sites.

NUDGE-FLU Analysis

Previously, the Danish found that electronic letters that nudged recipients to get vaccinated for influenza and also provided information on its cardiovascular benefits (so-called "gain-framing") were associated with a small increase of about 1% in flu vaccine uptake.

In this prespecified clinical outcome assessment of that trial, no statistically significant differences in clinical outcomes were found among those who received a letter that incorporated cardiovascular gain-framing or in those who received repeated letters, when compared with the usual care group who received no letters, reported Johansen and co-authors.

Hospitalization for pneumonia or influenza was 1% in the usual care group, 1% in the group that received the letters with cardiovascular gain-framing, and 1.1% in the repeated-letter group. Hospitalization for any cause was approximately 13% in all three groups. Mortality during the study occurred in 1.8% of the usual care group, 1.9% in the gain-framing group, and 1.7% in the repeated-letter group.

Given the modest results of the original NUDGE-FLU trial, the findings of the prespecified analysis came as no surprise to Mark Fendrick, MD, of the University of Michigan Medical School in Ann Arbor.

"It's not that the flu shot doesn't work, it's that an intervention that got a very small [number] of additional people to get the flu shot did not produce a positive outcome effect across the entire population," Fendrick told 麻豆传媒. "I would not expect an additional 1% of a population getting the flu shot to actually show meaningfully clinical outcome differences."

"There's pretty robust evidence to show that a lot of these [vaccine] reminders are not extraordinarily effective," he added.

Johansen told 麻豆传媒 via email that his group wasn't surprised either. "We were well aware that our nudging letters only resulted in modest increases in influenza vaccination, and we therefore suspected that the difference in vaccination rates would not be enough to drive a difference in clinical outcomes."

In the original NUDGE-FLU trial, approximately 965,000 Danish participants were randomized to usual care or to receive one of nine different electronically delivered behavioral nudging letters during the 2022-2023 flu season. The current analysis included 691,820 participants of that trial who were 65 years of age or older. Since the original NUDGE-FLU trial found that repeated standard letters and cardiovascular gain-framing letters resulted in modest but significantly higher rates of influenza vaccination, the current analysis focused on comparison of the groups that received no letters, letters sent at baseline and 14 days later, and cardiovascular gain-framed letters.

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