Objective: To investigate the characteristics of breakthrough cases of varicella in Haishu District, Ningbo City, Zhejiang Province from 2017 to 2022, so as to provide the evidence for varicella prevention and control. Methods: Information on reported cases of varicella and vaccination in Haishu District from 2017 to 2022 were collected through the China Infectious Disease Reporting Management Information System and the Immunization Program Information Management System of Zhejiang Province. The breakthrough cases who had received 1 or 2 doses of varicella vaccine 42 days before the onset of disease were selected. The distribution of sex, age, region and the interval between onset and last immunization were descriptively analyzed. Results: A total of 1 563 varicella cases were reported from 2017 to 2022. There were 928 breakthrough cases (59.37%), of which 660 cases with 1-dose immunization history (42.23%) and 268 cases with 2-dose immunization history (17.15%). The proportion of 1-dose breakthrough cases in total annual cases showed a decreasing trend (P<0.05) from 2017 to 2022, while there was no significant tendency on the proportion of cases with 2-dose immunization history (P>0.05). There were 392 males (59.39%) and 268 females (40.61%) with 1-dose immunization history. There were 150 males (55.97%) and 118 females (44.03%) with 2-dose immunization history. Breakthrough cases with 1- and 2- dose immunization history had an median age of 13.00 (interquartile range, 4.00) and 9.00 (4.00) years, respectively, and the difference was statistically significant (P<0.05). The regional distribution of the breakthrough cases with 1- and 2- dose immunization history was mainly in the rural-urban fringe, with 319 cases (48.33%) and 137 cases (51.12%), respectively, and the difference was statistically significant (P<0.05). The median interval between onset and last immunization was 12.00 (interquartile range, 3.00) and 4.00 (3.00) years, respectively, and the difference was statistically significant (P<0.05). Conclusions The breakthrough cases of varicella in Haishu District from 2017 to 2022 were mainly cases with 1-dose immunization history, males, and residents in rural-urban fringe. The age was older and the interval between onset and the last immunization was longer in cases with 1-dose immunization history than in cases with 2-dose immunization history.