No immunological interference or concerns about safety when seasonal quadrivalent influenza vaccine is co-administered with a COVID-19 mRNA-1273 booster vaccine in adults: A randomized trial

The objective of the study was to assess the safety and immunogenicity of mRNA-1273 COVID-19 booster vaccination when co-administered with an egg-based standard dose seasonal quadrivalent influenza vaccine (QIV). This was a phase 3, randomized, open-label study. Eligible adults aged >= 18 years were randomly assigned (1:1) to receive mRNA-1273 (50 mu g) booster vaccination and QIV 2 weeks apart (Seq group) or concomitantly (Coad group). Primary objectives were non-inferiority of haemagglutinin inhibition (HI) and anti-Spike protein antibody responses in the Coad compared to Seq group. 497/498 participants were randomized and vaccinated in the Seq/Coad groups, respectively. The adjusted geometric mean titer/concentration ratios (95% confidence intervals) (Seq/Coad) for HI antibodies were 1.02 (0.89-1.18) for A/H1N1, 0.93 (0.82-1.05) for A/H3N2, 1.00 (0.89-1.14] for B/Victoria, and 1.04 (0.93-1.17) for B/Yamagata; and 0.98 (0.84-1.13) for anti-Spike antibodies, thus meeting the protocol-specified non-inferiority criteria. The most frequently reported adverse events in both groups were pain at the injection site and myalgia. The 2 groups were similar in terms of the overall frequency, intensity, and duration of adverse events. In conclusion, co-administration of mRNA-1273 booster vaccine with QIV in adults was immunologically non-inferior to sequential administration. Safety and reactogenicity profiles were similar in both groups (clinicaltrials.gov NCT05047770). What is the context? Updated booster shots against COVID-19 disease are likely to offer more protection as the virus is changing over time.It is important for doctors, other healthcare providers and patients to know whether COVID-19 booster vaccines can be given at the same time as other vaccines recommended for adults.What is new? The results of our study showed that an mRNA-based COVID-19 booster vaccine could be given at the same time as the seasonal influenza vaccine.When given together, both vaccines led to immune responses and had side effects that were similar to those observed when they were given at separate times.What is the impact? The potential benefits of administering more than 1 vaccine during a healthcare visit include improved coverage and a reduced number of doctor visits needed to receive all vaccines.Co-administration of COVID-19 booster vaccines and influenza vaccines could be an attractive option for patients and healthcare professionals.