TY - JOUR
T1 - Electronic Nudges to Increase Influenza Vaccination in Immunosuppressed Adults Across the Age Spectrum
T2 - A Pooled Analysis of Two Nationwide Randomized Trials
AU - Reimer Jensen, Anne Marie
AU - Johansen, Niklas Dyrby
AU - Wolff, Peter Suldrup
AU - Vaduganathan, Muthiah
AU - Bhatt, Ankeet S
AU - Modin, Daniel
AU - Skaarup, Kristoffer Grundtvig
AU - Duus, Lisa Steen
AU - Chatur, Safia
AU - Claggett, Brian L
AU - Janstrup, Kira Hyldekær
AU - Hill, Joshua A
AU - Van Spall, Harriette G C
AU - Larsen, Carsten Schade
AU - Larsen, Lykke
AU - Wiese, Lothar
AU - Dalager-Pedersen, Michael
AU - Køber, Lars
AU - Solomon, Scott D
AU - Sivapalan, Pradeesh
AU - Jensen, Jens Ulrik Stæhr
AU - Martel, Cyril Jean-Marie
AU - Krause, Tyra Grove
AU - Biering-Sørensen, Tor
N1 - © The Author(s) 2026. Published by Oxford University Press on behalf of Infectious Diseases Society of America. All rights reserved. For commercial re-use, please contact [email protected] for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact [email protected].
PY - 2026/4/12
Y1 - 2026/4/12
N2 - BACKGROUND: Immunosuppressed individuals face higher risk of severe influenza complications, yet vaccination coverage remains low. We aimed to assess the effect of electronic letter-based nudges on influenza vaccination uptake by immunosuppression status.METHODS: We performed a participant-level pooled analysis of two methodologically harmonized, nationwide, pragmatic randomized clinical trials (NUDGE-FLU-2 and NUDGE-FLU-CHRONIC) conducted during the 2023-2024 influenza season. Adults aged ≥65 years (NUDGE-FLU-2) and adults aged 18-64 years with chronic conditions (NUDGE-FLU-CHRONIC) were included, with immunosuppression defined by an immunosuppressive diagnosis or a filled prescription for immunosuppressive therapy. Participants were randomized in a 2.45:1:1:1:1:1:1 ratio to usual care or one of six electronic letter interventions. The primary outcome was receipt of influenza vaccination by January 1, 2024, ascertained from nationwide administrative health registries. Effect modification by immunosuppression status was assessed using binomial regression.RESULTS: Among 1,181,254 participants (mean age 67 years; 73,830 [6.3%] immunosuppressed), 66.1% were vaccinated. Any letter increased vaccine uptake compared with usual care (absolute difference, 2.79 percentage points; 95% CI, 2.60-2.98; p<0.001), with greater effect among immunosuppressed individuals (+4.12 vs +2.70 percentage points; pinteraction=0.002). In younger adults with chronic conditions, letter-based nudges increased vaccination rates by 11.7 percentage points overall and by 13.3 percentage points among those with immunosuppression (pinteraction=0.007). Among immunosuppressed individuals, nudging effects appeared greater for those with immunosuppressive conditions than for those receiving immunosuppressive treatment.CONCLUSIONS: Electronic letter-based nudges increased influenza vaccination rates, with greater benefit among individuals with immunosuppression. These findings support implementation of low-cost, letter-based nudging strategies to improve vaccine uptake in this high-risk population.
AB - BACKGROUND: Immunosuppressed individuals face higher risk of severe influenza complications, yet vaccination coverage remains low. We aimed to assess the effect of electronic letter-based nudges on influenza vaccination uptake by immunosuppression status.METHODS: We performed a participant-level pooled analysis of two methodologically harmonized, nationwide, pragmatic randomized clinical trials (NUDGE-FLU-2 and NUDGE-FLU-CHRONIC) conducted during the 2023-2024 influenza season. Adults aged ≥65 years (NUDGE-FLU-2) and adults aged 18-64 years with chronic conditions (NUDGE-FLU-CHRONIC) were included, with immunosuppression defined by an immunosuppressive diagnosis or a filled prescription for immunosuppressive therapy. Participants were randomized in a 2.45:1:1:1:1:1:1 ratio to usual care or one of six electronic letter interventions. The primary outcome was receipt of influenza vaccination by January 1, 2024, ascertained from nationwide administrative health registries. Effect modification by immunosuppression status was assessed using binomial regression.RESULTS: Among 1,181,254 participants (mean age 67 years; 73,830 [6.3%] immunosuppressed), 66.1% were vaccinated. Any letter increased vaccine uptake compared with usual care (absolute difference, 2.79 percentage points; 95% CI, 2.60-2.98; p<0.001), with greater effect among immunosuppressed individuals (+4.12 vs +2.70 percentage points; pinteraction=0.002). In younger adults with chronic conditions, letter-based nudges increased vaccination rates by 11.7 percentage points overall and by 13.3 percentage points among those with immunosuppression (pinteraction=0.007). Among immunosuppressed individuals, nudging effects appeared greater for those with immunosuppressive conditions than for those receiving immunosuppressive treatment.CONCLUSIONS: Electronic letter-based nudges increased influenza vaccination rates, with greater benefit among individuals with immunosuppression. These findings support implementation of low-cost, letter-based nudging strategies to improve vaccine uptake in this high-risk population.
U2 - 10.1093/cid/ciag219
DO - 10.1093/cid/ciag219
M3 - Article
C2 - 41968745
SN - 1058-4838
JO - Clinical Infectious Diseases
JF - Clinical Infectious Diseases
ER -