High-dose Influenza Vaccine Consistently More Effective vs Standard-dose in Older Adults: Meta-analysis

In older adults, high-dose influenza vaccine was found to be significantly and consistently more effective compared to standard dose influenza vaccine in preventing influenza, emergency department (ED) visits, and hospital admissions for adverse influenza-related events, report authors of a new study presented during IDWeek 2022, held from October 19 to 23, in Washington, DC.

To determine the relative efficacy and effectiveness of high-dose influenza vaccines in the population aged ≥65 years. researchers conducted a systematic review and meta-analysis, identifying 19 studies (randomized controlled trials and observational studies) conducted over 11 consecutive influenza seasons from 2009 to 2020. The final pooled cohort numbered more than 45 million adults who had received either high- or standard-dose influenza vaccination.

According to the study abstract, receiving high-dose influenza vaccine was associated with greater relative efficacy and effecivenss vs receiving a standard-dose vaccine against probable or laboratory-confirmed influenza-like illnesses (14.3%; 95% CI, 4.2%-23.3%), hospital and ED visits (10.4%, 95% CI, 6.8%-13.9%), and influenza hospitalization (11.2%; 95% CI, 7.4%-14.8%).

High-dose influenza vaccines also conferred greater proection than standard-dose vaccines gainst hospitalizations for pneumonia (27.3%, 95% CI, 15.3-37.6%), against influenza and pneumonia (13.4%; 95% CI,7.3-19.2%), and against respiratory (14.3%; 95% CI, 8.5-20.0%), cardiovascular (13.1%; 95% CI, 10.5-15.7%), cardiopulmonary (17.9%; 95% CI, 15.0-20.8%), and all-cause events (8.4%; 95% CI, 5.7-11.0%).

Results favored high-dose influenza vacccine in subanalyses stratified by dominant influenza strain, antigenic match, and study design and setting, according to the abstract. Superior efficacy/effectiveness of high-dose influenza vaccines vs standard-dose vaccines against influenza and associated serious outcomes remained consistent regardless of participant age or characteristics of a specific flu season.

Results favored high-dose influenza vacccine in subanalyses stratified by dominant influenza strain, antigenic match, and study design and setting.

Further, in age-stratified analyses, all adults benefitted from receiving the high-dose vaccine but the study authors found that there was additional relative benefit of the vaccine with increasing age.

“Evidence over 11 consecutive influenza seasons from both randomized and observational studies suggest HD-IIV [high-dose influenza vaccination] was consistently more effective than SD-IIV [standard-dose influenza vaccination] at reducing influenza and associated serious outcomes irrespective of recipient age and characteristics of the influenza season,” the researchers concluded.

Reference: Lee JK, Lam GK, Vaisman R, et al. Efficacy and effectiveness of high-dose influenza vaccine in older adults by age and seasonal characteristics: An updated systematic review and meta-analysis. Poster presented at: IDWeek 2022; October 19-23, 2022; Washington, D.C.