High-dose influenza vaccine linked to reduced hospitalization risk in older adults

High-dose inactivated influenza vaccine (HD-IIV) confers improved protection against hospitalization outcomes for older adults when compared with standard-dose inactivated influenza vaccine (SD-IIV), according to the results of a meta-analysis.

Researchers searched multiple online databases for randomized clinical trials in which the efficacy of HD-IIV was compared with that of SD-IIV in adults aged ≥65 years. Outcomes included hospitalizations for influenza, laboratory-confirmed influenza (LCI), pneumonia or influenza, cardiorespiratory disease, and all causes and all-cause mortality.

Eight trials met eligibility criteria and were included in the meta-analysis. Five trials involved older adults from the general population, two trials enrolled nursing home residents (aged ≥65 years), and one trial included individuals with heart failure or history of myocardial infarction with no age restriction (mean age 65.5 years). The total study population comprised 605,098 participants. All trials were deemed to be at low risk of bias.

Pooled data showed that compared with SD-IIV, HD-IIV was associated with markedly lower hospitalizations for influenza (relative vaccine effectiveness [rVE], 38.5 percent), LCI (rVE, 31.2 percent), pneumonia or influenza (rVE, 11.5 percent), cardiorespiratory disease (rVE, 7.5 percent), and all causes (rVE, 3.3 percent).

Mortality outcomes did not significantly differ between HD-IIV and SD-IIV (rVE, 0.9 percent).

The findings were consistent across subgroup and sensitivity analyses.