The following is a summary of “Estimating standard-dose and high-dose Fluzone vaccine efficacies for influenza A based on HAI titers,” published in the December 2024 issue of Infectious Disease by Hammerton et al.
The high-dose (HD) Fluzone influenza vaccine is recommended for older adults (OAs) due to its superior antibody responses and vaccine efficacy (VE) compared to the standard dose (SD), however, the evolving nature of influenza strains necessitates ongoing VE monitoring, which is challenging due to the resource-intensive nature of traditional efficacy trials.
Researchers conducted a retrospective study to perform immunogenicity analyses on updated influenza vaccine formulations and estimate VE using hemagglutination inhibition (HAI) titers as a reliable correlate of protection.
They analyzed data from a human vaccine cohort who received either the SD or HD Fluzone split-inactivated influenza vaccine during the 2013/14 to 2021/22 influenza seasons. A previously developed statistical model was used to map pre- and post-vaccination HAI titers to protection probabilities and to compute differences in VE between the HD vaccine for individuals aged 65 and older and the SD vaccine in the same age group, as well as in younger adults (<65 years).
The results showed that for participants aged 65 and older, the HD vaccine generally enhanced the estimated VE across seasons. However, HD recipients often demonstrated a lower estimated VE compared to younger adults receiving the SD vaccine.
Investigators concluded the HD Fluzone vaccine in OAs demonstrated a slight increase in estimated VE compared to the SD.
Source: academic.oup.com/jid/advance-article-abstract/doi/10.1093/infdis/jiae615/7922923
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