Integration of high-dose flu vaccine in routine practice may show benefit in novel trial
Researchers in Denmark announced the successful completion of an “innovative” trial assessing effects of influenza vaccine dosages on hospitalizations using only routinely collected data.
The results of the open-label, randomized DANFLU-1 trial were presented at the European Society of Cardiology Congress.
“It’s estimated that 1 billion people worldwide are infected by influenza yearly,” Tor Biering-Sørensen, MD, PhD, MPH, professor of translational cardiology and pragmatic randomized studies in the department of biomedical sciences at Copenhagen University, Denmark, said during a press conference. “Influenza infection can cause cardiovascular events, and we know that the risk of cardiovascular events increases in the days after a positive influenza test. Furthermore, these increased risks can be decreased by influenza vaccination.”
In 2022, the vaccine program in Denmark is only offering the standard-dose vaccine, according to the presentation.
Biering-Sørensen added that several types of influenza vaccine exist, such as higher doses, and that these high-dose vaccines, although proved to significantly reduce risk for infection, may not be as widely implemented due to a lack of trial data evaluating them for reducing risk for death and hospitalization.
Therefore, researchers conducted the DANFLU-1 trial, and invited 34,000 individuals to participate. The trial was integrated into the Danish national vaccine program, only requiring one study visit for vaccination. Follow-up was completed using national health care registries through May 2022.
A total of 12,477 participants were enrolled to receive standard or high-dose influenza vaccine.
The primary outcome of the DANFLU-1 trial was trial feasibility, in terms of whether it was possible to conduct a trial integrating the Danish vaccination program and complete follow-up only using registry data. To this, Biering-Sørensen confirmed that the DANFLU-1 trial was successfully designed and executed, with 99.97% complete follow-up data.
The hypotheses-generating outcome of interest was incidence of influenza or pneumonia hospitalization, hospitalization for cardiorespiratory disease and all-cause mortality among individuals who received the high-dose influenza vaccine compared with standard dose.
Biering-Sørensen said the trial was not powered to definitively assess the effect of vaccine dose on these outcomes.
After a representative volume element analysis, researchers observed 64.4% lower cumulative incidence of influenza or pneumonia hospitalization (95% CI, 24.4-84.6), no difference in hospitalization for cardiorespiratory disease (12.1%; 95% CI, –15.5 to 33.3) and a 48.9% lower incidence of all-cause mortality (95% CI, 11.5-71.3) among those who received the high-dose vaccine compared with standard-dose vaccine.
“The DANFLU-1 trial was an innovative trial of influenza vaccines integrated into routine clinical practice where we randomized almost 12,500 participants. It relied only on routinely collected health care data,” Biering-Sørensen said during the press conference. “It provided us with a hint of benefit in morbidity and mortality with the high-dose [influenza] vaccine compared with the standard dose. A future large-scale trial could show whether high-dose influenza vaccines should be offered routinely and might reduce risk of hospitalizations.”
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Biering-Sørensen T, et al. Hot Line 2. Presented at: European Society of Cardiology Congress; Aug. 26-29, 2022; Barcelona, Spain (hybrid meeting).
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