Daily Dose: Coadministration of RSV and Flu Vaccines in Older Adults

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Patient Care brings primary care clinicians a lot of medical news every day—it’s easy to miss an important study. The Daily Dose provides a concise summary of one of the website's leading stories you may not have seen.

Last week, we reported on findings from an abstract presented at IDWeek 2023, held October 11-15 in Boston, MA.

The study

Investigators conducted the phase 3 study in older adults to compare the safety and immunogenicity of coadministration of the Pfizer bivalent, stabilized RSV prefusion F subunit vaccine (RSVpreF) and adjuvanted quadrivalent seasonal inactivated influenza vaccine (SIIV) with SIIV alone or RSVpreF alone. The investigation’s primary immunogenicity objective was to demonstrate noninferiority of coadministration of RSVpreF 120 µg with SIIV compared with sequential administration of SIIV followed by RSVpreF one month later.

Researchers defined a 1.5-fold equivalence margin. The safety profile of coadministration of RSVpreF with SIIV was evaluated by collection of reactogenicity and adverse events.

A total of 1403 healthy Australian adults aged 65 years and older were randomly assigned in a 1:1 ratio to coadministration or sequential administration of the 2 vaccines. The safety population of 1399 participants received vaccination at a median age of 70 years.

Findings

The investigators reported that the study met the primary immunogenicity objective. Specifically, the geometric mean ratios (GMRs) ranged from 0.85 to 0.86 for RSVpreF and 0.77 to 0.90 for SIIV, for RSV neutralizing titers and strain-specific hemagglutination inhibition assay titers at 1 month after vaccination, achieving the 1.5-fold prespecified non-inferiority margin (lower bound CI > 0.667).

Regarding safety outcomes, both local reactions and systemic adverse events were mostly mild or moderate when RSVpreF was coadministered with SIIV. There were no vaccine related serious adverse events reported.

Authors' comment

"The primary objectives of the study were met demonstrating noninferiority of the RSVpreF and SIIV immune responses when RSVpreF was coadministered with SIIV, and that RSVpreF had an acceptable safety profile when coadministered with SIIV. The results of this study support the coadministration of RSVpreF and SIIV in an older adult population."

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