Beijing Center for Disease Control and Prevention, Beijing, PR China.
Vaccine. 2012 Jul 20;30(34):5094-8. doi: 10.1016/j.vaccine.2012.05.072. Epub 2012 Jun 9.
Varicella vaccine is available in the private sector in China, with a single dose currently recommended for children aged ≥12 months. We investigated a varicella outbreak in a school in Beijing with high varicella vaccination coverage to describe the outbreak, examine risk factors for vaccine failure, and calculate vaccine effectiveness.
A varicella case was defined as an acute generalized maculopapular rash without other apparent cause in a student without prior varicella attending the elementary school during August 30-December 28, 2010. Varicella among vaccinated students (breakthrough varicella) was defined as varicella occurring >42 days after vaccination. Students' vaccination status was verified with immunization records and clinical presentations were collected from health care practitioners.
Of the 951 students, 934 (98%) had no prior varicella history. Among these students, 916 had received 1 dose of varicella vaccine and 2 had received 2 doses (98% vaccination coverage) before the outbreak. A total of 87 cases occurred during the outbreak; most had breakthrough varicella (86/87, 99%) and mild disease (83/87, 95%). Age at vaccination (<15 months vs. ≥15 months) and time since vaccination before outbreak (<5 years vs. ≥5 years) were not associated with development of breakthrough varicella. Single-dose varicella vaccination was 89% effective in preventing any varicella and 99% in preventing moderate/severe varicella.
Single-dose varicella vaccination is highly effective in reducing varicella incidence and mitigating disease severity, but not high enough to prevent outbreak. A two-dose program might help to prevent varicella outbreaks in Beijing.
水痘疫苗在中国的私营部门中可获得，目前建议 12 个月及以上儿童接种一剂。我们调查了北京一所学校的水痘暴发，该学校的水痘疫苗接种率很高，以描述暴发情况，研究疫苗失败的危险因素，并计算疫苗效力。
水痘病例定义为在 2010 年 8 月 30 日至 12 月 28 日期间，在没有先前水痘史的小学生中，急性全身性斑丘疹，无其他明显病因。接种疫苗的学生（突破性水痘）定义为接种疫苗后 >42 天发生的水痘。通过免疫记录验证学生的疫苗接种状况，并从保健医生处收集临床症状。
在 951 名学生中，934 名（98%）无先前的水痘病史。在这些学生中，916 名接受了 1 剂水痘疫苗，2 名接受了 2 剂（98%的疫苗接种率），然后暴发了。暴发期间共发生 87 例，其中大部分为突破性水痘（86/87，99%），病情较轻（83/87，95%）。接种年龄（<15 个月与≥15 个月）和暴发前接种疫苗的时间（<5 年与≥5 年）与突破性水痘的发生无关。一剂水痘疫苗接种对预防任何水痘的有效性为 89%，对预防中度/重度水痘的有效性为 99%。
一剂水痘疫苗接种可有效降低水痘发病率和减轻疾病严重程度，但不足以预防暴发。两剂疫苗接种计划可能有助于预防北京的水痘暴发。
