Abstract
As China implements the voluntary vaccination programme of one-dose of varicella vaccine (VarV) for decades, robust estimates of the impact of voluntary vaccination era on epidemiology of varicella are needed. We estimated the vaccination coverage (VC) of VarV by using surveillance data on immunisation. The descriptive epidemiological method was used to describe the changing epidemiology of varicella from 2007 to 2018. The screening method was used to estimate the vaccine effectiveness (VE) of VarV. The overall VC for VarV was 71.7%, ranged from 47.7% to 79.5% among 2008-2017 birth cohorts. In total, 16 660 varicella cases were reported during 2007-2018, the incidence increased from 10.0 cases per 100 000 population in 2007 to 65.2 cases per 100 000 population in 2018. A shift in age group of varicella was observed since 2012, with the age increased from 5-9 years to 10-14 years. The overall VE was 79.9%, and the VE increased from 60.1% in 2008 birth cohort to 96.2% in 2017 birth cohort. We found that the overall VE for VarV is moderate, but appears highly effective within 5 years after vaccination. In addition, a shift varicella infection to older ages has occurred at the long-term moderate level VC of one-dose VarV. Therefore, to contain the incidence of varicella and prevent any potential shift to older ages, the introduction of VarV into routine immunisation programme is likely needed in Lu'an.
Highlights
Varicella is highly contagious disease caused by varicella-zoster virus primary infection and endemic to all countries worldwide
Data in this stage consisted of three parts: (1) extraction of varicella vaccination information in children born in 2008–2017 birth cohorts from Anhui Immunization Information Management System (AIIMS), (2) extraction of varicella cases that occurred in children born in 2008–2017 birth cohorts from CISDCP and (3) verify their vaccination status via matching names, date of birth, name of parents or address in the AIIMS
In the first stage of the study, we aimed to evaluate the vaccination coverage (VC) of varicella vaccine (VarV) and compare the coverage of VarV with the coverage of the second dose of measles containing vaccine (MCV2), which had been introduced in Expanded Program on Immunization (EPI) since 2008
Summary
Varicella is highly contagious disease caused by varicella-zoster virus primary infection and endemic to all countries worldwide. Similar to many other vaccine preventable diseases, active immunisation is considered one of the most effective intervention for varicella. The live attenuated Oka strain varicella vaccine (VarV) was first developed in 1974 by Takahashi in Japan and has turned out to be safe and effective at preventing varicella [2]. There are only 36 countries and regions that have introduced VarV for routine immunisation, few of them implemented a two-dose schedule currently [4]. This may due to concerns about cost-effectiveness, a shift in disease to older ages and an increase in herpes zoster in the elderly [1, 4]
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