The purpose of this study is to evaluate the immunogenicity and safety of Northern hemisphere 2013-2014 seasonal trivalent inactivated influenza vaccine in 60 healthy infants aged 6-35 months old, 60 healthy adults aged 18-60 years old, and 60 healthy seniors aged > 60 years.

For adults and seniors:

Inclusion Criteria:

• Healthy adults aged 18-60 years old, and healthy seniors aged > 60 years old;
• Without vaccination history of seasonal split influenza vaccine in the recent 3 years
• No traveling plan during the study period of this trial;
• Be able to understand and sign the informed consent;

Exclusion Criteria:

• Allergic to egg products or any ingredient of the study vaccine;
• Fever, influenza or acute illness on the vaccination day;
• Acute stage of chronic illness;
• Malignant tumor;
• Immunodeficiency, includes HIV infection;
• Guillain-Barre syndrome;
• Administration of live attenuated vaccine within the previous 14 days;
• Administration of subunit or inactivated vaccine within the previous 7 days;
• Planned to participate in any other clinical trial of drug or vaccine during this study;
• Received immunesuppressive treatment within the previous month, or planned for such treatment during this study;
• Pregnant, or planning pregnancy;
• Axillary temperature > 37.0℃;
• Any other factors that, in the judgment of the investigator, is unsuitable for this study;

For infants:

Inclusion Criteria:

• Healthy male or female aged between 6 and 35 months;
• Full-term birth, birth weight 2,500 grams or more;
• Provided birth certification or vaccination card
• Parent or legal guardian is able to understand and sign the informed consent;

Exclusion Criteria:

• Received seasonal influenza vaccine after June 30, 2012;
• Acute infection within the previous week;
• Allergy history, or allergic to any ingredient of the study vaccine, such as egg;
• History of serious adverse reaction (SAR) to vaccine;
• Autoimmune disease or immune deficiency, or administration of immunosuppressive therapy, cell toxic therapy, or inhaled corticosteroid within the previous 6 months;
• Congenital malformations, developmental disorder or serious chronic disease;
• Unstable condition of asthma and administration of corticosteroid in the most recent two years;
• Coagulation abnormalities or disorders;
• History/ family history of infantile convulsion, epilepsy, cerebropathy, or mental disease;
• Without spleen;
• Severe neurological diseases, such as Guillain-Barre syndrome;
• Administration of blood products or investigational drug within the previous month;
• Administration of live attenuated vaccine within the previous 14 days;
• Administration of subunit or inactivated vaccine within the previous 7 days;
• Received treatment for allergy within the previous 14 days;
• on-going anti-tuberculosis therapy;
• Axillary temperature > 37.0℃ immediately before vaccination;
• any other factors that, in the judgment of the investigator, is unsuitable for this study;