Department of Microbiology & Parasitology, Faculty of Medical Sciences, National Autonomous University, León, Nicaragua.
Epidemiology, Biostatistics and Prevention Institute, University of Zürich.
J Infect Dis. 2016 Nov 15;214(10):1498-1506. doi: 10.1093/infdis/jiw411. Epub 2016 Sep 6.
Universal 2-dose hepatitis A virus (HAV) vaccination of toddlers effectively controls hepatitis A. High vaccine costs, however, impede implementation in endemic countries. To test single-dose vaccination as a possible alternative, we initiated an observational, longitudinal study in Nicaragua, to assess protective effectiveness and-through challenge vaccination-humoral immune memory response.
After a 2003 serosurvey, 130 originally seronegative children received one dose of virosomal HAV vaccine in 2005, followed by yearly serological and clinical assessments until 2012. After 7.5 years, a vaccine booster was administered. Concurrent antibody screening of patients presenting with hepatitis symptoms documented persistent HAV circulation in the communities studied.
Between serosurvey and vaccination, 25 children contracted hepatitis A subclinically (>8000 mIU/mL anti-HAV). In the remaining 105 children, immunization resulted in anti-HAV levels of 17-572 mIU/mL. Based on the ≥15% annual infection risk, an estimated 60% of children were exposed to HAV encounters during follow-up. No child presented with hepatitis symptoms. Serological breakthrough infection (7106 mIU/mL) was documented in 1 child, representing an estimated protective effectiveness of 98.3% (95% confidence interval, 87.9-99.8). Boosting elicited an average 29.7-fold increase of anti-HAV levels.
In children living in hyperendemic settings, a single dose of virosomal HAV vaccine is sufficient to activate immune memory and may provide long-term protection.
为了有效控制甲型肝炎，给幼儿接种两剂通用型甲型肝炎病毒（HAV）疫苗。然而，疫苗费用高昂，阻碍了在流行地区的实施。为了检验单剂疫苗接种作为一种可能的替代方法，我们在尼加拉瓜启动了一项观察性、纵向研究，评估保护效力，并通过挑战疫苗接种评估体液免疫记忆反应。
在 2003 年进行血清调查后，130 名最初血清阴性的儿童在 2005 年接受了一剂病毒体 HAV 疫苗，随后每年进行血清学和临床评估，直到 2012 年。7.5 年后，进行了疫苗加强接种。同时对出现肝炎症状的患者进行抗体筛查，证明研究社区中持续存在甲型肝炎病毒传播。
在血清调查和疫苗接种之间，有 25 名儿童亚临床感染了甲型肝炎（抗-HAV 抗体>8000 mIU/mL）。在其余 105 名儿童中，免疫接种导致抗-HAV 水平为 17-572 mIU/mL。根据每年>15%的感染风险，估计在随访期间有 60%的儿童接触到了 HAV 。没有儿童出现肝炎症状。有 1 名儿童发生了血清学突破性感染（7106 mIU/mL），估计保护效力为 98.3%（95%置信区间，87.9-99.8）。加强接种可使抗-HAV 水平平均增加 29.7 倍。
在生活在高度流行地区的儿童中，一剂病毒体 HAV 疫苗足以激活免疫记忆，并可能提供长期保护。
