Epidemiology of varicella and effectiveness of varicella vaccine in Jinan, 2006-2022.

Objective To analyze the epidemiological characteristics of varicella and effectiveness of varicella vaccine in Jinan. Methods We collected data of varicella surveillance in Jinan from 2006 to 2022 from the Chinese Information System for Disease Control and Prevention and vaccination data for children born during 2010-2021 form the Jinan Immunization Planning Information System. All reported varicella cases from 2006 to 2022 in Jinan were analyzed with descriptive epidemiological methods; Coverage and effectiveness of varicella vaccine for children born during 2010 to 2021 were conducted with the screening method. Results 61 145 cases of varicella were reported in Jinan during 2006-2022, yielding an annual average incidence of 51.82 per 100 000 population; the incidence ranged from 74.48 per 100 000 in 2008 to 28.47 per 100 000 in 2022. Peak varicella incidences occurred between April and June and between November and the following January. The highest incidence rate was 5-9 years old group from 2006-2016 and was 15-19 years old group from 2017 to 2022. Coverage levels for one doses was 77.32% in the 2010-2021 births; the overall effectiveness of varicella vaccine was 91.83% (95%CI: 91.43%-92.30%). Coverage levels for two doses was 45.86% in the 2010-2018 births; the overall effectiveness of varicella vaccine was 95.14%(95%CI: 94.56%-95.66%). Conclusion The high incidence age group shifted from 5-9 years old to 15-19 years old. It was suggested that the vaccine administration should be used to targeted age groups. Levels of vaccine effectiveness for 2 doses of varicella vaccine were greater than levels of Vaccine effectiveness for one-doses. We suggest to introduce 2 dose of varicella vaccine into the national immunization program for children. [ABSTRACT FROM AUTHOR]