Durham, NC—Many older Americans remain uncertain of which influenza vaccine they should receive each year, since public health officials show no strong preference for the high-dose flu shot as opposed to the standard one. Should they?

That was the question addressed in a new study published in JAMA Network Open that examined the comparative safety, reactogenicity, and short-term effects of vaccination on health-related quality of life after trivalent adjuvanted inactivated influenza vaccine (aIIV3) or trivalent high-dose inactivated influenza vaccine (HD-IIV3) in adults aged 65 years and older.

In the randomized clinical trial of 757 older adults (378 receiving aIIV3 and 379 receiving HD-IIV3), Duke University Medical Center–led researchers determined that the proportion of participants with moderate-to-severe injection-site pain (primary outcome) was not higher after aIIV3 than HD-IIV3. Furthermore, no vaccine-related serious adverse events occurred, and postvaccination health-related quality of life was similar between the aIIV3 and IIV3-HD groups.

“These findings suggest that from a safety standpoint, aIIV3 or HD-IIV3 is an acceptable option to prevent influenza in older adults,” they conclude.

The article points out that aIIV3 and HD-IIV3 are U.S.-licensed for adults aged 65 years and older, adding that data was needed on the comparative safety, reactogenicity, and health-related quality of life (HRQOL) effects of these vaccines.

The randomized, blinded clinical trial was conducted at multiple U.S. centers during the 2017 to 2018 and 2018 to 2019 influenza seasons. Participants were community-dwelling adults aged at least 65 years and assessed for eligibility; most, 55%, were women, and 78% were of white race with a median age of 72 years. They received IM administration of aIIV3 or HD-IIV3 after age-stratification—age 65 to 79 years or 80 years and older—and randomization.

Researchers focused on proportions of participants with moderate-to-severe injection-site pain and 14 other solicited reactions during days 1 to 8, using a noninferiority test (5% noninferiority margin), and serious adverse events (SAE) and adverse events of clinical interest (AECI), including new-onset immune-mediated conditions, during days 1 to 43. They also compared changes in HRQOL scores before and after vaccination (days 1, 3) between study groups.

Results indicate that the proportion reporting moderate-to-severe injection-site pain limiting or preventing activity, after aIIV3 (12 participants [3.2%]) (primary outcome), was noninferior compared with HD-IIV3 (22 participants [5.8%]) (difference -2.7%; 95% CI, -5.8-0.4). The authors report that 10 reactions met noninferiority criteria for aIIV3, while 4 (moderate-to-severe injection-site tenderness, arthralgia, fatigue, malaise) did not, with it being inconclusive whether those reactions occurred in higher proportions of participants after aIIV3. No participant sought medical care for a vaccine reaction, and no adverse effects of clinical interest were observed.

While nine participants had at least one serious adverse effect after aIIV3 (2.4%; 95% CI,1.1%-4.5%) and three had at least one SAE after HD-IIV3 (0.8%; 95% CI, 0.2%-2.2%), none were found to associated with vaccination. Furthermore, changes in prevaccination and postvaccination HRQOL scores were not clinically meaningful and not different between the groups, the researchers advise.

“Overall safety and HRQOL findings were similar after aIIV3 and HD-IIV3, and consistent with prelicensure data. From a safety standpoint, this study’s results support using either vaccine to prevent influenza in older adults,” the authors conclude.

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