Abstract: Objective To evaluate the safety of EV71 vaccine in Zhejiang province. Methods Based on the results of active and passive monitoring and using the AEFI subsystem, the data on AEFI related to EV71 vaccine in Zhejiang province from Jan 1, 2016 to Dec 31, 2019 was collected and analyzed with descriptive epidemiological methods. Results 1 830 cases of AEFI following EV71 vaccination were reported in Zhejiang province over the four years and the estimated incidence was 72.23 per 100 000 doses. Among them, 202 cases of abnormal reactions were reported and the incidence was estimated to be 7.97 per 100 000 doses. The ratio of males to females was 1.17:1 among these cases. 81.92% of the cases of AEFI involved patients between 6 and 24 months old. 51.53% of the cases occurred between April and July. 1 283 cases (70.11%) of adverse reactions started after the first dose and 1 180 cases (64.48%) within one day of vaccination. The symptoms of common adverse reactions ranged from fever, local swelling, induration to anaphylactic rashes. 79.45% of the cases of AEFI eventually recovered. Conclusion EV71 vaccine used in Zhejiang province is safe. Active monitoring is more sensitive than passive monitoring, but monitoring methods need to be optimized.

Key words: EV71 vaccine, safety, methods for monitoring, AEFI