Safety Study of Quadrivalent Subunit Influenza Vaccine in People Aged 3 Years and Older

This is a large-scale, multicenter, open-label, single-arm, non-controlled real-world safety observational study following influenza vaccination. It is designed to assess the occurrence of very rare adverse reactions (incidence <0.01%) following vaccination with a quadrivalent influenza subunit vaccine and to demonstrate its superior safety profile.

A total of 42,881 participants aged 3 years and above were enrolled. Each received a single 0.5 ml dose of the quadrivalent influenza subunit vaccine. Safety monitoring included immediate observation for 30 minutes post-vaccination and systematic surveillance over the subsequent 28 days. Data on adverse events (AEs) and serious adverse events (SAEs) were collected during two time intervals: from 30 minutes to 7 days (inclusive) and from 8 to 28 days (inclusive) after vaccination. Any newly identified adverse reactions during the study period were also recorded.

Inclusion criteria

• Healthy individuals aged 3 years or above.
• The participant (and/or their guardian/legal representative) has provided informed consent, voluntarily agreed to participate, signed the Informed Consent Form, and is able to comply with the requirements of this study protocol.

Exclusion criteria

• Individuals with a known allergy to any component of the vaccine, including eggs, excipients, formaldehyde, or Triton N-101.
• Individuals suffering from an acute illness, severe chronic disease, an acute exacerbation of a chronic disease, common cold, or fever.
• Individuals with uncontrolled epilepsy or other progressive neurological disorders, or a history of Guillain-Barré syndrome.
• Any other condition considered by the investigator as inappropriate for participation in this study.