In a randomised, double-blind Australian study, antibody responses and likelihood of adverse events were similar whether the two vaccines were coadministered or given sequentially.

Respiratory syncytial virus (RSV) vaccination is now recommended, with shared decision-making, for adults aged 60 years or older. As both RSV and influenza are seasonal infections; coadministration of these vaccines has been proposed to eliminate the need for a second healthcare visit. However, concerns have been raised that this approach could blunt the immune response to both vaccines while also causing higher rates of adverse events. In a manufacturer-supported, randomised, double-blind trial from April to October of 2022, Australian investigators compared concurrent versus sequential administration of the bivalent prefusion F glycoprotein RSV vaccine (ABRYSVOTM) and the quadrivalent seasonal inactivated influenza vaccine (Fluad Quad), with each vaccine being given one month apart. In all, 1403 participants aged 65 years or older were enrolled; those with a serious chronic disorder were excluded.

One month after immunisation, the geometric mean ratios (GMRs) of antibody responses to concurrent vs sequential vaccination for the two RSV and four influenza antigens ranged from 0.77 to 0.90. Thus, all responses to coadministered vaccines were lower than those to sequential administration but above the GMR of 0.67 prespecified as noninferior. Local and systemic adverse event rates were similar with coadministered or sequential vaccination.

Comment: While these results demonstrated that concurrent vaccination for RSV and influenza was not inferior to sequential administration, the trial excluded patients with underlying conditions – the very patients most likely to receive both vaccines and in whom protection is most needed. Because of this study limitation, I would not endorse this approach for individuals with underlying illnesses until more data are available; furthermore, I would administer vaccinations at least two weeks apart in such patients.

Neil M. Ampel, MD, Professor Emeritus of Medicine, University of Arizona; Supplemental Consultant, Mayo Clinic in Arizona, Phoenix, USA.

Athan E, et al. Safety and immunogenicity of bivalent rsvpref vaccine coadministered with seasonal inactivated influenza vaccine in older adults. Clin Infect Dis 2023 Nov 22; e-pub (https://doi.org/10.1093/cid/ciad707).

This summary is taken from the following Journal Watch titles: Infectious Diseases, Ambulatory Medicine, General Medicine, Hospital Medicine.