A Centralized Outbreak of Varicella among Children Attending Preschool in Suzhou, China

Abstract

Background. Varicella vaccine is available for voluntary purchase with a single dose currently recommended for children aged ≥12 months. An epidemiological study was undertaken in order to determine the characteristics of the outbreak, assess vaccine effectiveness, and examine risk factors for vaccine failure. Methods. A varicella case was defined as a generalized papulovesicular rash (without other apparent causes) in a child without prior varicella attending the kindergarten during February 22 to April 7 of 2016. Varicella among vaccinated children (breakthrough varicella) was defined as varicella occurring >42 days after vaccination. Children’s vaccination status was verified with immunization records through local vaccination information platform. Results. Of the 738 children, 664 (90.0%) had no prior varicella history. Of these, 364 (54.8%) had received a single-dose varicella vaccine before outbreak. A total of 30 cases occurred in the outbreak, and 9 of them (30%) had breakthrough varicella. Age at vaccination (<15 months vs. ≥15 months) and time since vaccination before the outbreak (<3 years vs. ≥3 years) were not related to the occurrence of breakthrough varicella (P>0.05). Single-dose varicella vaccination was 64.7% effective in preventing any varicella. Conclusions. Single-dose varicella vaccine is effective in reducing the varicella attack rate, but not high enough to prevent outbreak. Timely detection and effective isolation are key factors in controlling varicella. Improving single-dose vaccination coverage and implementing two-dose vaccination strategy should be recommended to provide excellent protection to prevent varicella in the future in Suzhou.

Immunogenicity and Safety of a Booster Dose of Live Attenuated Varicella Vaccine, and Immune Persistence of a Primary Dose for Children Aged 2 to 6 Years

“…Though the universal varicella vaccination has led to a reduction in morbidity and mortality resulting from varicella infection in the USA, active surveillance data from sites and states with well-implemented vaccination programs indicate that the number of reported varicella cases remains constant or has declined minimally [ 7 ]. However, outbreaks of varicella in schools with high vaccine coverage rate are often reported [ 8 ]. Considering that a single dose has been shown to be effective in reducing the incidence of severe varicella, this schedule has been associated with breakthrough disease [ 9 , 10 ] caused by primary vaccine failure and the declining exogenous exposure from children shedding wild-strain VZV [ 11 ].…”

Vaccination against Varicella Zoster Virus Infection in Less Developed Regions of Guangdong, China: A Cross-Sectional Serosurveillance Study

“…At present, most cities in China still implement a one-dose VarV program. An archived study showed that one-dose VarV is not enough to prevent outbreaks of varicella [ 49 ]. A two-dose VarV procedure has been introduced in a few cities, e.g., Beijing in 2012 and Hangzhou in 2014 [ 38 ].…”

National and provincial burden of varicella disease and cost-effectiveness of childhood varicella vaccination in China from 2019 to 2049: a modelling analysis

“…Varicella could cause high economic and psychological burdens to individuals, families, and society. 13 , 14 In China, varicella vaccination was firstly used in 1998. 15 A systematic review found varicella vaccination coverage among children was about 61% in China in 2017.…”