A71-11 Relative Effectiveness of High-Dose vs. Standard-Dose Inactivated Influenza Vaccine in Older Adults With Chronic Lung Disease
L S Duus, N D Johansen, D Modin, M M Loiacono, R C Harris, Y Huang, C S Larsen, L Larsen, L Weise, M Dalager-Pedersen, B L Claggett, K H Janstrup, K V Bartholdy, K F Bernholm, J I H Borchsenius, F S Davidovski, L W Davodian, M Dons, A R Jensen, C Espersen, F H Fussing, N E Landler, A C F Langhoff, M C H Lassen, A B Nielsen, C I Ottosen, M Sengeløv, K G Skaarup, S D Solomon, M J Landray, G H Gislason, L Køber, P Sivapalan, C J Martel, J S Jensen, T Biering-SørensenAbstract
Rationale
Seasonal influenza vaccination is recommended for individuals with chronic conditions, including those with chronic lung disease (CLD), who are especially susceptible to influenza-related complications. This prespecified analysis sought to assess the relative vaccine effectiveness (rVE) of high-dose (HD-IIV) vs. standard-dose (SD-IIV) inactivated influenza vaccine against endpoints in older adults with CLD.
Methods
DANFLU-2 was a pragmatic individually-randomized trial of adults ≥65 years assigned 1:1 to HD-IIV or SD-IIV during the 2022-2025 influenza seasons. Data were obtained from the nationwide administrative health registries. Follow-up ran from 14 days post-vaccination to May 31 the following year. CLD was defined by the presence of an ICD-10 code (A15-16, D860, E84, J42-47, J84, or Z942) at baseline. The primary endpoint was hospitalization for pneumonia or influenza; prespecified secondary endpoints included hospitalizations for influenza, cardiorespiratory, and any cause. Exploratory endpoints included hospitalizations for cardiovascular, respiratory, laboratory-confirmed influenza.
Results
Of 332,438 participants (166,218 randomized to HD-IIV and 166,220 to SD-IIV), 27,152 (8.2 %) had CLD. Participants with CLD were older, had more comorbidities, and higher hospitalization rates than those without CLD. Among participants in the SD-IIV group, incidence rates for outcomes were higher among participants with chronic lung disease than those without (primary outcome: 45.8 vs. 9.1 events/1,000 participant-years). HD-IIV did not significantly reduce the primary outcome of hospitalization for influenza or pneumonia compared with SD-IIV (overall rVE 6%, 95% CI -2% to 13%). However, HD-IIV was associated with fewer influenza hospitalizations (overall rVE 36%, 95% CI 22% to 47%), with consistent effects by CLD status (rVE 42%, 95% CI: 21% to 57% in CLD; vs. 48%, 95% CI 17% to 68% in no CLD, p-interaction = 0.67). Overall absolute rate reduction was higher in those with CLD than those without. In addition, HD-IIV was associated with fewer cases of laboratory-confirmed influenza hospitalizations (rVE 32%, 95% CI 23% to 40%). Here, potential effect modification by CLD status was observed (rVE 26%, 95% CI 15% to 35% vs 47%, 95% CI 31% to 60%; p-interaction = 0.03) (Figure). No evidence of potential effect modification was observed for other endpoints assessed. FLUNITY-HD results, pooling DANFLU-2 with the harmonized GALFLU study, will be available.
Conclusion
Among older adults, HD-IIV was associated with lower risk of influenza hospitalization and of laboratory-confirmed influenza hospitalization than SD-IIV in participants with and without CLD, indicating important public health value and greater absolute benefit for this population at high risk of influenza-related complications.
This abstract is funded by: The trial was funded by Sanofi.