Division of Infectious Diseases and Global Public Health, University of California-San Diego, La Jolla, California, USA.
Division of Infectious Diseases and Geographic Medicine, Department of Medicine, Stanford University, Stanford, California, USA.
Clin Infect Dis. 2024 Apr 10;78(4):976-982. doi: 10.1093/cid/ciad552.
Widespread outbreaks of person-to-person transmitted hepatitis A virus (HAV), particularly among people who inject drugs (PWID), continue across the United States and globally. However, the herd immunity threshold and vaccination coverage required to prevent outbreaks are unknown. We used surveillance data and dynamic modeling to estimate herd immunity thresholds among PWID in 16 US states.
We used a previously published dynamic model of HAV transmission calibrated to surveillance data from outbreaks involving PWID in 16 states. Using state-level calibrated models, we estimated the basic reproduction number (R0) and herd immunity threshold for PWID in each state. We performed a meta-analysis of herd immunity thresholds to determine the critical vaccination coverage required to prevent most HAV outbreaks among PWID.
Estimates of R0 for HAV infection ranged from 2.2 (95% confidence interval [CI], 1.9-2.5) for North Carolina to 5.0 (95% CI, 4.5-5.6) for West Virginia. Corresponding herd immunity thresholds ranged from 55% (95% CI, 47%-61%) for North Carolina to 80% (95% CI, 78%-82%) for West Virginia. Based on the meta-analysis, we estimated a pooled herd immunity threshold of 64% (95% CI, 61%-68%; 90% prediction interval, 52%-76%) among PWID. Using the prediction interval upper bound (76%) and assuming 95% vaccine efficacy, we estimated that vaccination coverage of 80% could prevent most HAV outbreaks.
Hepatitis A vaccination programs in the United States may need to achieve vaccination coverage of at least 80% among PWID in order to prevent most HAV outbreaks among this population.
甲型肝炎病毒（HAV）在人与人之间广泛传播的爆发，尤其是在注射毒品者（PWID）中，仍在美国和全球范围内持续发生。然而，尚不清楚预防爆发所需的群体免疫阈值和疫苗接种覆盖率。我们使用监测数据和动态模型来估计美国 16 个州的 PWID 中的群体免疫阈值。
我们使用先前发表的甲型肝炎病毒传播的动态模型，该模型根据涉及 16 个州的 PWID 的暴发监测数据进行了校准。使用州级校准模型，我们估计了每个州的 PWID 的基本繁殖数（R0）和群体免疫阈值。我们对群体免疫阈值进行了荟萃分析，以确定预防大多数 PWID 中甲型肝炎爆发所需的关键疫苗接种覆盖率。
HAV 感染的 R0 估计值从北卡罗来纳州的 2.2（95%置信区间[CI]，1.9-2.5）到西弗吉尼亚州的 5.0（95%CI，4.5-5.6）。相应的群体免疫阈值从北卡罗来纳州的 55%（95%CI，47%-61%）到西弗吉尼亚州的 80%（95%CI，78%-82%）。基于荟萃分析，我们估计 PWID 的总体免疫阈值为 64%（95%CI，61%-68%；90%预测区间，52%-76%）。使用预测区间上限（76%）并假设 95%的疫苗效力，我们估计 80%的疫苗接种覆盖率可以预防大多数甲型肝炎爆发。
为了预防该人群中的大多数甲型肝炎爆发，美国的甲型肝炎疫苗接种计划可能需要在 PWID 中实现至少 80%的疫苗接种覆盖率。
