The clinical trial was designed to evaluate the immunogenicity and safety against pediatric Inactivated influenza vaccine (Split Virion) (0.25ml formulation) of Hualan administered on infants age 6 months to 36 months.

The clinical trial was designed randomized and double-blind. Participants included up to 810 persons (540 persons in test group and 270 persons in control group).

Healthy 6-36 months infants were selected, whose guardians were volunteers and had signed the informed consent. Subjects were selected according to the inclusion and exclusion criteria. Every subject accepted 30min's observation in the hospital after vaccination and received periodic follow-up till the fourth week after the boost vaccination.

Blood of subjects was collected at the third week after the boost vaccination for the analysis of the immunogenicity. During the test, the adverse reactions and detailed information were reported to the SFDA under the status of blinding every month. Unblinding was conducted after the completion of the follow-up of subjects.

Inclusion Criteria:

• Infants aging 6-36 months, their guardians understand and sign the informed consent
• Healthy infant by inquiring illness history, physical examination and clinical judgment and who complies with vaccination of this product
• Be able to comply with the requirement of clinical trial protocol
• Have no history of vaccination within the past 6 months and vaccination with other product within the latest 1 week
• Axillary temperature ≤37.0℃.

Exclusion Criteria:

1. Exclusion criteria for primary vaccination:

   • History of other vaccine or immunoglobulin inoculation within 2 weeks
   • History of eclampsia, epilepsy, encephalopathy and mental disease or family disease
   • History of vaccination allergy or allergy to drug and food (egg)
   • Known or suspected immunological function defects, including immunosuppressant therapy (radiotherapy, chemotherapy, corticosteroid hormone, antimetabolites, cytotoxic drug), genetic defects (favism), HIV infection or other reasons
   • Congenital malformation, maldevelopment or serious chronic disease (such as Down syndrome, diabetes, sickle cell anemia or neurologic disease)
   • Acute and chronic contagion, active infection (history of fever within the past 3 days (axillary temperature ≥38.0℃) or acute disease needing application of antibiotics or anti-virus treatment in the whole body)
   • Organic diseases such as liver, kidney, serious cardiovascular disease
   • Malignancy (tumor), serious asthma
   • Thrombopenia or other coagulopathy that may cause contraindication of intramuscular injection
   • Any condition resulting in the absence or removal the spleen
   • Hypertension (not including the higher blood pressure below 150mmHg and lower blood pressure below 100mmHg controlled by drug)
   • Participating in another clinical trial or any condition that, in the judgment of investigator, may affect trial assessment.

2. Exclusion criteria for a boost vaccination:

   • Any condition in the "Exclusion criteria" of the first injection after inclusion
   • Adverse reactions level 3 or above within 72 hours after first vaccination;
   • Serious adverse reactions having casual relationship with the first inoculation of test vaccine
   • Subjects are not willing to be inoculated any more and quit
   • Axillary temperature ≥37℃ before immunization
   • Reasons that can not conduct inoculation, in the judgment of investigators.