High-dose flu vaccine maintains efficacy in older adults with chronic CVD
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Key takeaways:
- Chronic CVD did not modify the efficacy of the high-dose influenza vaccine against hospitalizations for pneumonia or influenza and all-cause mortality in older adults.
- More research is needed.
High- vs. standard-dose influenza vaccine was linked to a lower incidence of mortality and hospitalizations for pneumonia or influenza regardless of chronic CVD, according to a study presented at the European Society of Cardiology Congress.
The findings were simultaneously published in Circulation: Cardiovascular Quality and Outcomes.
As Healio previously reported, researchers announced the successful completion of the DANFLU-1 trial and reported lower cumulative incidence of influenza or pneumonia hospitalization and all-cause mortality, but they found no difference in hospitalization for cardiorespiratory disease among those who received the high-dose vaccine compared with the standard-dose vaccine. Despite these findings, the trial was not powered to definitively assess the effect of vaccine dose on these outcomes.
“We sought to assess whether the presence of several CV diseases modified the relative effectiveness of [high-dose vs. standard-dose quadrivalent influenza vaccine] with regard to clinical outcomes,” Jacob Christensen, MB, of the department of cardiology at Copenhagen University Hospital — Herlev and Gentofte in Denmark, and colleagues wrote in the simultaneous publication.
To do this, Christensen and colleagues conducted a prespecified analysis of the DANFLU-1 trial, which included 12,477 adults aged 65 to 79 years (mean age, 71.7 years; 47.1% women) in Denmark.
The CVDs assessed by the researchers included HF, ischemic heart disease, atrial fibrillation and a combined group denoted as “chronic CVD” which consisted of all these diseases in addition to heart valve disease, stroke, peripheral artery disease, congenital heart disease and others.
Researchers randomly assigned participants in a 1:1 ratio to high-dose (QIV-HD) and low-dose (QIV-SD) quadrivalent influenza vaccine, both of which contained the four influenza strains recommended by WHO for the 2021-2022 influenza season, according to the researchers.
Prespecified outcomes included hospitalizations due to pneumonia or influenza, respiratory disease, cardiorespiratory disease, CVD, all-cause hospitalizations and all-cause mortality.
They also conducted a secondary, exploratory analysis of participants with chronic CVD to assess whether recency of hospitalizations prior to randomization in the study modified the relative effectiveness of QIV-HD compared with QIV-SD.
Overall, 20.4% of participants had chronic CVD, 7.7% had ischemic heart disease, 7% had AF and 2.2% had HF.
Median follow-up was 237 days (interquartile range, 232-239).
Results again showed QIV-HD reduced the incidence of hospitalizations and mortality compared with QIV-SD.
Importantly, the researchers also found that the presence of chronic CVD did not modify the effect of QIV-HD vs. QIV-SD against hospitalizations for pneumonia or influenza, as seen by similar incidence rate ratios [IRR] overall (0.3; 95% CI, 0.14-0.64) and for those with chronic CVD (IRR = 0.44; 95% CI, 0.1-1.93) and no chronic CVD (IRR = 0.26; 95% CI, 0.11-0.64; P for interaction = .57). The same pattern occurred for all-cause mortality (overall: HR = 0.51; 95% CI, 0.3-0.86; chronic CVD: HR = 0.38; 95% CI, 0.14-1.06; no chronic CVD, HR = 0.58; 95% CI, 0.31-1.08; P for interaction = .49).
The presence of chronic CVD did, however, lessen the relative effectiveness of QIV-HD compared with QIV-SD against all-cause hospitalizations, with an IRR of 0.87 (95% CI, 0.76-0.99) overall and 0.79 (95% CI, 0.67-0.92) for no chronic CVD, compared with 1.11 (95% CI, 0.88-1.39) for chronic CVD (P for interaction = .026)
However, the presence of HF, ischemic heart disease and atrial fibrillation did not modify the effect of QIV-HD against all-cause mortality or hospitalizations compared with QIV-SD, according to the researchers.
“As such, high-dose influenza vaccine might still be beneficial in patients with CVD, particularly in prevention of respiratory disease endpoints for which it is primarily indicated,” the researchers wrote.
Additionally, the secondary, exploratory analysis revealed that time since latest all-cause hospitalization prior to randomization among patients with chronic CVD modified the effect of QIV-HD compared with QIV-SD against all-cause hospitalizations, with QIV-HD not being favored in patients with more recent hospitalization (P = .03).
“This result suggests that the relative effectiveness of QIV-HD might attenuate with more recent hospitalization, which in turn might support the notion that a high baseline event rate could dilute the effectiveness of high-dose influenza vaccine,” the researchers wrote.
The researchers acknowledged several study limitations, including that the DANFLU-1 trial was not specifically powered for clinical outcomes; therefore, “these findings should be regarded as hypothesis-generating,” they wrote.
Reference:
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Christensen J, et al. Cardiovascular outcome studies in the elderly. Presented at: European Society of Cardiology Congress; Aug. 30-Sept. 2, 2024; London (hybrid meeting).
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