March 05, 2020
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High-dose flu vaccine provides greater protection for older adults

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Influenza vaccination over the course of two influenza seasons in the United States demonstrated low to moderate efficacy for the prevention of influenza-related hospitalizations among adults aged 65 years and older, according to findings published in Clinical Infectious Diseases.

“Each year, seasonal influenza causes substantial disease and mortality in older adults in the United States,” Jill M. Ferdinands, PhD, epidemiologist in the Influenza Division, CDC, told Healio. “Unfortunately, previous studies have shown that older adults mount less robust immune responses to influenza vaccination. High-dose influenza vaccines contain more antigen that standard influenza vaccines — four times the antigen — and were developed for use among people 65 years of age and older for the purpose of improving influenza vaccine response in this age group.”

Ferdinands and colleagues conducted an observational vaccine effectiveness study of patients hospitalized with acute respiratory illness at eight hospitals in the U.S. Hospitalized Adult Influenza Vaccine Effectiveness Network during the 2015-2016 and 2016-2017 influenza seasons to evaluate how well influenza vaccines, including high-dose influenza vaccines, prevent influenza hospitalization among older adults.

Patients enrolled in the study were tested for influenza and the researchers recorded receipt and type of influenza vaccine. Effectiveness was then estimated for both the standard dose and the high dose of the vaccine via a test-negative design, which compared the odds of influenza among vaccinated vs. unvaccinated patients.

Among the cohort of 1,487 patients aged 65 years and older, 1,107 (74%) were vaccinated; 622 (56%) received the high-dose inactivated influenza vaccine (HD-IIV) and 485 (44%) received the standard-dose influenza vaccines (SD-IIV).

In all, 277 (19%) of patients tested positive for influenza, including 98 patients (16%) who received HD-IIV, 87 (18%) who received SD-IIV and 92 (24%) who were unvaccinated.

After adjusting for confounding variables, Ferdinands and colleagues found that the effectiveness of SD-IIV was 6% (95% CI, 42% to 38%) and the effectiveness of HD-IIV was 32% (95% CI, 3% to 54%). This translated to a relative effectiveness of HD-IIV vs. SD-IIV of 27% (95% CI, 1% to 48%).

These findings support other vaccine effectiveness studies that show that high-dose influenza vaccines provide better protection than standard dose influenza vaccines for people 65 years of age and older.

“People 65 years and older can get any influenza vaccine approved for use in that age group,” Ferdinands said. “The Advisory Committee on Immunization Practice (ACIP) does not currently recommend any vaccine over another for this age group. When updating recommendations, ACIP examines the whole body of evidence regarding high-dose vaccine.” – by Caitlyn Stulpin

Disclosures: Ferdinands reports no relevant financial disclosures. Please see the full study for all other authors’ relevant financial disclosures.