Immunogenicity of Concomitant Administration of COVID-19 Vaccines With Influenza Vaccines

This was an open-label, randomized clinical trial conducted at the International St. Mary's Hospital in Incheon, South Korea. This study included two study groups: Concomitant administration of omicron containing messenger ribonucleic acid (mRNA) COVID-19 booster and quadrivalent influenza vaccination (QIV) and separate administration of influenza vaccination followed by mRNA booster ≥4 weeks later * immunogenicity analysis : Blood was drawn at baseline and follow-up visit 4 weeks, 3 months, 6 months, 10-12 months after immunization(For the COVID-19 vaccine, additional blood sampling will be conducted one week after vaccination). * 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.