To monitor the safety of Beijing Tiantan Biological's influenza vaccine in elderly through Adverse Events Following Immunization Surveillance System of China.

The hypothesis is that there is no significant difference in the occurrence of adverse events among influenza vaccines manufactured by independent companies.

In 2011 and 2012, Beijing Municipal Health Bureau launched the free influenza vaccination campaign among children aged 6-18 years old and the elderly aged 60 years old and above. Inactivated split-virion vaccines from Beijing Tiantan Biological Products Company were used for the elderly in the campaign.

All vaccine recipients provided written informed consent, containing information about the vaccine, possible adverse effects, and medical care.

Adverse events were collected through the National Immunization Information System's National Adverse Events Following Immunization (AEFI) Surveillance System, which was established in 2005 on the basis of World Health Organization (WHO) guidelines. According to the Guideline for the Identification of Adverse Reaction after Immunization issued by the Chinese Ministry of Health in 2008, Beijing CDC and local prefectural CDC must organize an expert panel to investigate adverse events and assess causality, using criteria based on Chinese Standard Procedures for Vaccination. The panels consist of physicians, epidemiologists, pharmacists, and other relevant experts. In general, expert panels investigate deaths, life-threatening illnesses, and permanent disabilities, and immunization-program managers or vaccination providers investigate common, minor adverse events. Adverse events are classified into one of five categories: vaccine reactions (common and minor to rare and more serious), program errors, coincidental illnesses, psychogenic reactions, and unclassifiable events.

At the time of vaccination, vaccinees were instructed to report any adverse event to physicians or vaccination providers. Adverse events that were fatal or that resulted in disability and clusters of events (i.e., notably high numbers of similar adverse events related to a certain vaccine) were required to be reported within 2 hours after their occurrence. The following adverse events were required to be reported within 2 days after their occurrence: anaphylaxis or other allergic reactions occurring within 24 hours after vaccination; fever (axillary temperature, >37.5°C), angioedema, or a local injection-site reaction (diameter, >2.5 cm) occurring within 5 days after vaccination; purpura, an Arthus reaction, febrile convulsion, seizure, or polyneuritis occurring within 15 days after vaccination; and the Guillain-Barré syndrome occurring within 3 months after vaccination. Other reactions that were common and minor (e.g., mild pain and fatigue) were not required to be reported.

Inclusion Criteria:

1. Males and females aged 60 years and above on the day of immunization, who are eligible for seasonal influenza vaccination.
2. In the judgement of the study doctor are determined to be in reasonable health considering their age and able to comply with all study procedure.

Exclusion Criteria:

1. History of any serious reaction to flu vaccine, or any materials in the vaccine, and to eggs (including ovalbumin) and chicken protein.
2. Receipt of a live vaccine within 4 weeks prior to Study Day 1.
3. Any condition, which in the opinion of the study doctor, might interfere with the evaluation of the study objective.

Beijing subjects aged 60 years or older, at the time of routine visit to a participating clinic or hospital for annual influenza vaccination.