Westmead, Australia—Influenza vaccines are administered to millions of people across the globe to reduce morbidity and mortality from influenza. A new report notes that, as new vaccine formulations are increasingly used, the need to monitor and compare their safety, as well as efficacy, is essential.

A report in JAMA Network Open addresses whether the 2018 adjuvanted trivalent inactivated influenza vaccine (TIIV) and high-dose TIIV were associated with adverse events in Australian recipients aged 65 years or older.

Researchers from The Children’s Hospital at Westmead and colleagues sought to assess the postmarketing safety profile of 2018 Southern Hemisphere influenza vaccines, especially the two new enhanced trivalent inactivated influenza vaccines.

To do that, they conducted a cohort study using solicited short message service–based, self-reported survey data on adverse events occurring within 3 to 5 days after receipt of an influenza vaccination.

Participants were older adults who received routinely recommended influenza vaccines at one of 265 sentinel immunization sites, including primary care, hospital, and community-based clinics. All sites participated in Australia’s AusVaxSafety active vaccine safety surveillance system from April 1 to August 31, 2018. Data were analyzed from September 1, 2018, to June 30, 2019.

The analysis considered any licensed 2018 influenza vaccine administered in clinical practice, determining rates—overall, by brand, and by concomitant vaccine receipt—of adverse events, including medical attendance as a proxy for serious adverse events.

Researchers advise that, of 72,013 individuals aged 65 years or older who received an influenza vaccine in 2018, 50,134 individuals (69.6%) responded to the initial survey regarding adverse events experienced after vaccination (median [interquartile range] age, 71 [68-76] years; 27,056 [54.0%] women).

While most of the respondents received an enhanced trivalent inactivated influenza vaccine, including 28,003 individuals (55.9%) who received aIIV3 and 19,306 individuals (38.5%) who received HD-IIV3; 2,208 of them (4.4%) received a quadrivalent inactivated influenza vaccine.

Recipients of HD-IIV3 reported significantly higher rates of any adverse event compared with those who received aIIV3—(1,716 [8.9%] vs. 1,796 individuals [6.4%]; P <.001). The same was true for specific adverse events, including fever (195 [1.1%] vs. 164 [0.6%]; P <.001), injection-site pain (383 [2.1%] vs. 350 [1.3%]; P <.001), and injection site swelling or redness (256 [1.4%] vs. 248 [0.9%]; P <.001).

At the same time, adverse-event rates reported by those receiving any quadrivalent inactivated influenza vaccine were similar to rates reported by those receiving aIIV3.

The authors note that rates of medical=care seeking for adverse events associated with aIIV3 and HD-IIV3 were low and comparable (80 individuals [0.3%] vs. 56 individuals [0.3%]; P = .91).

“The findings of this large-scale participant-based post marketing assessment of the safety of two new enhanced influenza vaccines used in individuals 65 years or older provide reassuring near-real-time and cumulative data to inform and support confidence in ongoing vaccine use,” the researchers conclude.

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