Nishiura H, Eichner M
Dept. of Medical Biometry, University of Tübingen, Westbahnhofstr. 55, Tubingen, Germany.
Infection. 2006 Oct;34(5):241-6. doi: 10.1007/s15010-006-6603-5.
Understanding the loss of vaccine-induced immunity against smallpox is essential in determining the fraction of those who are still protected in the present population and in constructing effective countermeasures against bioterrorist attacks.
Three small Australian outbreaks from the 1880s to early 1900s were investigated. Each documented individual age at infection. The case records for Launceston, 1903, further documented the age at vaccination and disease severity, enabling estimates of the duration of protection against severe and fatal smallpox.
A significant association between vaccination and death was observed in the outbreak in Sydney, 1881 (odds ratio of death among vaccinated individuals = 0.3; 95% confidence interval (CI): 0.1, 0.8; p = 0.02), where the time since last vaccination was similar for all vaccinated cases. In Launceston, 1903, where the age at vaccination varied widely, the median duration of partial protection against severe and fatal smallpox was estimated to be 31.7 (95% CI: 13.2, 116.2) and 53.9 (95% CI: 25.6, 123.5) years after vaccination, respectively. Whereas those in their 20s are expected to have the highest frequency of vulnerability to smallpox death in the present population, infections among those in their 30s or 40s are expected to be much less fatal.
Long lasting partial protection was suggested from the outbreak records, the estimated durations of which were roughly consistent with those reported previously. In the event of a bioterrorist attack, those involved in emergency tasks before emergency vaccination practices are re-established should ideally be previously vaccinated individuals in their 30s or 40s.
了解疫苗诱导的天花免疫力丧失情况对于确定当前人群中仍受保护的比例以及构建针对生物恐怖袭击的有效应对措施至关重要。
对19世纪80年代至20世纪初澳大利亚的三起小规模疫情爆发进行了调查。每起疫情都记录了感染时的个体年龄。1903年朗塞斯顿的病例记录进一步记录了接种疫苗的年龄和疾病严重程度，从而能够估计针对严重和致命天花的保护持续时间。
在1881年悉尼的疫情爆发中，观察到接种疫苗与死亡之间存在显著关联（接种疫苗个体的死亡比值比 = 0.3；95%置信区间(CI)：0.1，0.8；p = 0.02），所有接种疫苗的病例距离上次接种的时间相似。在1903年的朗塞斯顿，接种疫苗的年龄差异很大，接种疫苗后针对严重和致命天花的部分保护的中位持续时间分别估计为31.7年（95%CI：13.2，116.2）和53.9年（95%CI：25.6，123.5）。虽然预计20多岁的人群在当前人群中感染天花死亡的频率最高，但预计30多岁或40多岁人群的感染致死率要低得多。
疫情爆发记录表明存在持久的部分保护，其估计持续时间与先前报告的大致一致。在发生生物恐怖袭击的情况下，在重新建立紧急疫苗接种措施之前参与紧急任务的人员理想情况下应是先前接种过疫苗的30多岁或40多岁的人。
