Researchers have found that high-dose influenza vaccine (HD-IV) significantly reduces the rates of pneumonia and influenza (P&I) and all-cause hospitalizations in adults aged 65 and older compared to the standard-dose influenza vaccine (SD-IV). This study provides crucial insights into the relative effectiveness of HD-IV, particularly for severe clinical outcomes. This study was published in the Journal Of Infection by Kristoffer G. and colleagues.

Influenza poses a significant health risk, especially for older adults, leading to severe complications such as pneumonia and increased hospitalizations. This study aimed to summarize the current evidence on the effectiveness of HD-IV versus SD-IV in mitigating these severe outcomes in the elderly population. The study's objective was to assess whether HD-IV offers superior protection against P&I hospitalizations, all-cause hospitalizations, and all-cause death compared to SD-IV.
A prespecified meta-analysis was conducted, encompassing five randomized controlled trials with a total of 105,685 participants aged 65 years and older. The analysis evaluated the relative vaccine effectiveness (rVE) of HD-IV versus SD-IV using fixed-effects models with the inverse variance method. The primary outcomes measured were the rates of P&I hospitalization, all-cause hospitalization, and all-cause death
• HD-IV was associated with a 23.5% reduction in P&I hospitalizations compared to SD-IV (rVE: 23.5%, [95% CI: 12.3% to 33.2%]).
• The rate of all-cause hospitalizations was reduced by 7.3% in the HD-IV group compared to the SD-IV group (rVE: 7.3%, [95% CI: 4.5% to 10.0%]).
• No significant difference was observed in all-cause death rates between HD-IV and SD-IV (rVE: 1.6%, [95% CI: -2.0% to 5.0%]).
The findings suggest that HD-IV is more effective than SD-IV in reducing severe clinical outcomes like P&I and all-cause hospitalizations in adults aged 65 and older. The consistent protection across different subgroups underscores the importance of considering HD-IV for elderly populations, especially during flu seasons with high rates of complications. Despite the lack of significant difference in all-cause death rates, the reduction in hospitalization rates is a compelling argument for the use of HD-IV.
Sensitivity analyses, which omitted trials with participants sharing the same comorbidity, trials with 100 or more events, and using random-effects models, yielded comparable estimates for all outcomes, reinforcing the robustness of the findings.
This study concludes that HD-IV significantly reduces the incidence of P&I and all-cause hospitalizations compared to SD-IV in adults aged 65 and older. While no significant difference was observed in all-cause death rates, the evidence supports the use of HD-IV to mitigate severe clinical outcomes in the elderly. These findings, drawn from several randomized trials, highlight the potential benefits of HD-IV and suggest the need for further research in fully powered, individually randomized trials.
Reference:
Skaarup, K. G., Lassen, M. C. H., Modin, D., Johansen, N. D., Loiacono, M. M., Harris, R. C., Lee, J. K. H., Dufournet, M., Vardeny, O., Peikert, A., Claggett, B., Solomon, S. D., Jensen, J. U. S., & Biering-Sørensen, T. (2024). The relative vaccine effectiveness of high-dose vs standard-dose influenza vaccines in preventing hospitalization and mortality: A meta-analysis of evidence from randomized trials. The Journal of Infection, 106187, 106187. https://doi.org/10.1016/j.jinf.2024.106187