The goal is to evaluate the immunogenicity and safety of coadministration of a bivalent BA.4/BA.5-adapted COVID-19 booster vaccine, and influenza vaccine among healthy adults during 2022-23 season.

This was an open-label, non-randomized clinical trial conducted at the International St. Mary's Hospital in Incheon, South Korea. This study included two study groups: Concomitant administration of bivalent BA.4/BA.5 mRNA COVID-19 booster and quadrivalent influenza vaccination (QIV) and separate administration of influenza vaccination followed by bivalent BA.4/BA.5 mRNA booster ≥4 weeks later

• immunogenicity analysis : Blood was drawn at baseline and follow-up visit 4 weeks (day 28±7) after immunization.
• safety analysis : At 7 days after each vaccine dose, the participants were requested to record the occurrence, severity of solicited adverse events (AEs) through a standardized electronic questionnaire. Participants were also asked to record any unsolicited AEs during the 28 days after vaccination.

Inclusion Criteria:

• who agreed to receive both bivalent booster COVID-19 vaccine and influenza vaccine
• Only individuals who had passed at least 3 months after the last confirmation of SARS-CoV-2 infection and/or the third dose of COVID-19 vaccination

Exclusion Criteria:

• Individuals with a contraindication to any of the vaccine compounds were excluded from the study