The quadrivalent influenza vaccine usually requires only one injection. Quadrivalent influenza vaccine is a self-funded vaccination, which is based on the normal group A and C influenza vaccines, with the addition of group Y and W135 influenza vaccines. Usually, only one injection is needed, and it can achieve a higher preventive effect against pathogenic microorganisms with a wider range of preventive effects compared with the normal free influenza vaccine. If the patient has not received the Group A and C influenza vaccines, the patient can receive the normal injection directly. If the patient has been vaccinated with Group A and Group C vaccines, he/she should take the quadrivalent encephalitis vaccine three months after the vaccination interval. If the patient has not yet received the full dose of Group A and C influenza vaccine, the next dose of Group A and C influenza vaccine is not required after receiving the quadrivalent influenza vaccine. Common adverse reactions to QIV vaccine are fever, redness and swelling at the injection site, drowsiness, etc. They usually disappear about three days after the vaccination and do not require special treatment. Even if you receive the quadrivalent influenza vaccine, it does not prevent 100% of viral infections, you need to pay attention to personal hygiene and strengthen your own immunity in your normal living environment.