With the new RSV vaccines, there have been a couple of concerns. Earlier studies suggested that there might be a higher risk of side effects when they are given together. A new study suggests that is not a problem. The other concern is that the response rate to the individual vaccines may be less than if they were given separately. This study indicates that though the response was slightly less when given concurrently, it was not statistically significant. The term used her is noninferior. For those not familiar with the term, here is a definition.
By definition, a non-inferiority trial aims to demonstrate that the test product is not worse than the comparator by more than a small pre-specified amount.
The comments at the end of the summary I think are worth noting. The people that are most likely to get both vaccines together, the immunocompromised, were not included in the trial.
December 6, 2023
Concurrent Administration of RSV and Influenza Vaccines Appears Safe in Healthy Older Adults
Neil M. Ampel, MD, reviewing
In a randomized, 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. 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, randomized, double-blind trial from April to October of 2022, Australian investigators compared concurrent versus sequential administration of the bivalent prefusion F glycoprotein RSV vaccine (ABRYSVO™) and the quadrivalent seasonal inactivated influenza vaccine (Fluad Quad), with each vaccine being given 1 month apart. In all, 1403 participants aged ≥65 were enrolled; those with a serious chronic disorder were excluded.
One month after immunization, 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.
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 2 weeks apart in such patients.
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)