Simultaneous adjuvant flu, RZV vaccines a safe, ‘acceptable option’ for older adults

Key takeaways:

• Only 11.5% of adults given simultaneous administration of RZV and aIIV4 had one or more severe reactions.
• Severe adverse events were also infrequent among all study participants.

The simultaneous administration of adjuvant zoster and influenza vaccines posed no additional safety risks in older adults, results from a randomized study showed.

Study participants who received both adjuvanted recombinant zoster vaccine (RZV) and quadrivalent adjuvanted inactivated influenza vaccine (aIIV4) during the same visit had similar adverse reaction rates as those who received RZV in tandem with the quadrivalent high-dose inactivated influenza vaccine (HD-IIV4).

According to Kenneth E. Schmader, MD, a professor of medicine at Duke University School of Medicine, and colleagues, the CDC Advisory Committee on Immunization Practices has recommended since 2022 that adults aged 65 years or older receive one of the quadrivalent HD-IIV4, quadrivalent recombinant influenza vaccine or aIIV4.

“Vaccines with novel adjuvants are more reactogenic than vaccines without adjuvants, and there is a theoretical possibility that novel adjuvants could activate immune-mediated disease in some individuals,” they wrote in JAMA Network Open. “For older adults, the need for safety data on simultaneous administration of vaccines with novel adjuvants has specific clinical relevance.”

No clinical trials to date have examined the safety of simultaneous administration of aIIV4 with the adjuvanted RZV, they added.

In the randomized blinded clinical trial, the researchers assigned 267 adults aged 65 to 92 years to either simultaneous administration of aIIV4 and RZV or HD-IIV4 and RZV during the 2021-2022 and 2022-2023 influenza seasons.

The proportion of those who experienced one or more severe reactions during the first 8 days after vaccination measured with a noninferiority test served as the study’s primary outcome.

Schmader and colleagues found that 11.5% of patients who received simultaneous administration of RZV and aIIV4 reported one or more severe reactions compared with 12.5% of those who received simultaneous RZV and HD-IIV4 (absolute difference = 1%; 95% CI, 8.9% to 7.1%).

Only a few participants experienced serious adverse events, and the number of these were not significantly different between the two treatment groups.

Researchers also reported similar health-related quality-of-life scores for both groups. Schmader and colleagues identified several study limitations.. The number of Black and The number of Hispanic participants in the study population was small, hurting the general applicability of the findings, whereas the overall sample was too small for the researchers to detect rare serious adverse events.

“Vaccine safety active surveillance systems could be used to assess the frequency of rare safety events, including immune-mediated disease, among older adults receiving aIIV and RZV,” the researchers suggested.

They concluded that the findings show that the simultaneous administration of RZV and aIIV4 “was an acceptable option for vaccine delivery among older adults.”