Coadministration of the respiratory syncytial virus vaccine mRNA-1345 with seasonal influenza or COVID-19 vaccines demonstrated acceptable safety profiles and mostly noninferior immunogenicity in a phase III randomized trial of adults aged 50 years or older.
In a study published in The Lancet Infectious Diseases, researchers conducted two trial phases involving 3,314 participants across the United States between April and September 2022. In part A, they coadministered mRNA-1345 with a standard-dose quadrivalent influenza vaccine (SIIV4) to 685 participants, whereas 249 of them received mRNA-1345 alone and 689 of them received SIIV4 alone. Part B involved 564 participants who received mRNA-1345 with a bivalent COVID-19 vaccine (mRNA-1273.214), while 558 and 559 participants received mRNA-1345 or mRNA-1273.214 alone, respectively. Immunogenicity endpoints were evaluated at 29 days postvaccination.
The study revealed no significant safety concerns. Reactogenicity profiles were consistent between coadministered and individual vaccines, with no vaccine-related serious adverse events or fatalities reported during the follow-up period. The researchers noted that the reactogenicity profiles of the coadministered regimens were generally similar to the profiles when the vaccines were administered alone.
In terms of immunogenicity, coadministration showed mostly noninferior immune responses. For RSV-A neutralizing antibodies (nAbs), the geometric mean titer (GMT) ratios in coadministered vs individual groups were 0.81 (95% confidence interval [CI] = 0.67–0.97) in part A and 0.80 (95% CI = 0.70–0.90) in part B.
However, the seroresponse rate difference for RSV-A nAbs in part A did not meet the noninferiority criterion, falling at –11.2% (95% CI = –17.9 to –4.1). For influenza vaccine components, the GMT ratios for hemagglutination inhibition (HAI) titers against four strains ranged from 0.89 to 0.97, meeting the noninferiority threshold.
Coadministered mRNA-1345 plus SIIV4 or mRNA-1273.214 vaccines had acceptable safety profiles and elicited mostly noninferior immune responses compared with individual vaccines in adults aged 50 years or older. Only the seroresponse rate difference in nAbs against RSV-A in part A did not meet the noninferiority criterion, according to lead study author Jaya Goswami, MD, and her colleagues.
The findings suggested that combining vaccines could simplify immunization schedules for older adults, potentially improving uptake and reducing health care visits. The researchers supported the coadministration of mRNA-1345 with these vaccines in this population. They noted that longer-term evaluation is currently ongoing in this study.
The study was funded by Moderna, the manufacturer of the mRNA-1345 vaccine under evaluation, and several authors are affiliated with the company. These affiliations and funding support are disclosed, allowing for transparency in the interpretation of the findings. No additional conflicts of interest were reported.
