Objective To monitor the safety of an influenza A (H1N1) vaccination during 2009-2010 in Changning District of Shanghai.
Methods The data on adverse events following immunization (AEFI) were collected following a mass influenza A (H1N1) vaccination through a passive surveillance system and an active surveillance using questionnaire and telephone interview among students and teachers of 4 elementary and middle schools.
Results A total of 86 934 influenza A (H1N1) vaccine shots were administered during the study period in this district. The reported AEFI incidence through the passive surveillance system was 53.04 per 100 000, with the adverse events incidence of 8.25 per 100 000. A group of 2 092 influenza A (H1N1) vaccine shots were administered in the 4 elementary and middle schools. The reported AEFI incidence through the active surveillance system was 8 221.80 per 100 000, which was higher than that through the passive surveillance significantly. The syndromes reported by AEFI were mainly fever, local reaction and discomfort. The leading moderate adverse event was allergy. No severe adverse event was reported.
Conclusion The events failed to report are mainly mild symptoms. The reported influenza A (H1N1) vaccine is considered safe in a large scale of inoculation.
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