Coadministration of RSV, Influenza Vaccines is Safe and Effective in Older Adults, Study Finds

This article is part of our IDWeek 2023 coverage. You can find all of our news here.

Coadministration of the Pfizer bivalent RSVPref vaccine against respiratory syncytial virus (RSV) with the company’s adjuvanted quadrivalent seasonal inactivated influenza vaccine (SIIV) in adults aged 65 years and older was determined to be safe and effective, according to data presented at IDWeek 2023, in Boston, MA.

Reporting on findings from a phase 3 clinical trial during an oral abstract session titled New Developments in Vaccines, investigators said that immune responses to the vaccines administered simultaneously were noninferior to administration of either shot alone.

RSV and influenza cocirculate in a seasonal pattern with peaks during the winter in temperate climates, researchers note in the study abstract. Older adults are vulnerable to severe disease from both viruses. The US Centers for Disease Control and Prevention recommend annual vaccination with high-dose or adjuvanted influenza vaccine formulations to prevent influenza illness in older adults, study authors commented. Vaccination against RSV will be available for the first time during the 2023-2024 respiratory virus season, offering an opportunity to protect those aged 60 and older from lower respiratory tract illness based on a shared decision-making conversation with clinicians.

The current study was conducted as part of Pfizer’s phase 3 clinical trial program. 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 (range 65-91 years).

RESULTS

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, according to the study.

Source: Baber JA, Quan K, Athan E, et al. Coadministration of bivalent respiratory syncytial virus (RSVpreF) vaccine with influenza vaccine in older adults. Abstract presented at IDWeek 2023; October 11-15, 2023; Boston, MA.