At the time of vaccination, vaccinees were instructed to report any adverse event to physicians or vaccination providers. The following adverse events were required to be reported: 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) ; 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.