Vaccine mandates featuring a deadline, i.e. time-limited, can raise uptake either by pulling forward vaccinations that would have occurred later or by inducing additional vaccinations that would not have occurred absent the mandate. This paper asks how such mandates change vaccination behaviour, how the overall effect decomposes into the pull-forward and induction components, and which features of the mandate and public-health context drive that composition. Empirically, we study a low-coercion time-limited mandate targeting graduating high-school students in Western Australia and identify its causal effects using regression discontinuity designs based on strict school-age eligibility rules, applied to population-wide administrative records on first-dose COVID-19 vaccinations. We estimate both a static RDD at the deadline and a dynamic RDD that estimates the treatment effect over time. The mandate increased short-run first-dose uptake by 9.3 percentage points (12.7%) among the targeted cohort, but the dynamic evidence shows that this effect is entirely driven by pull-forward behavior: uptake converges in the long run, implying no vaccinations were induced. Students advanced vaccination by up to 80 days. Theoretically, we develop a simple present-bias model of vaccination under deadlines. We use it to interpret the empirical patterns and to derive, among other results, conditions under which time-limited mandates are more likely to pull forward vaccinations rather than inducing them. Our findings highlight the importance of evaluating mandates beyond short-run windows and provide a framework for designing and interpreting time-limited vaccination policies. Keywords: mandate; vaccination; incentives; uptake; adolescents; timing; coverage. JEL: I12; I18.

翻译：摘要：具有截止日期（即时限性）的疫苗强制政策可通过两种方式提升接种率：一是将原本会延后发生的疫苗接种提前（提前效应），二是诱导在无此强制政策情况下不会发生的额外疫苗接种（诱导效应）。本文探讨此类政策如何改变接种行为、总体效应如何分解为提前效应与诱导效应，以及政策特征与公共卫生情境如何决定该效应构成。实证研究中，我们分析了澳大利亚西部一项针对高中毕业生的低强制力时限性强制政策，并基于严格的学龄资格规则，采用断点回归设计（RDD）对覆盖全人群的首次新冠疫苗接种行政记录数据进行因果识别。我们同时估计了截止日期处的静态RDD和评估随时间变化的治疗效应动态RDD。该政策使目标群体的短期首次接种率提升9.3个百分点（12.7%），但动态证据表明该效应完全由提前行为驱动：长期接种率趋同，意味着未产生诱导效应。学生将接种时间提前了最多80天。理论层面，我们构建了截止日期下疫苗接种的简易现时偏差模型，用于解释实证规律，并推导出（包括其他结论在内）时限性强制政策更易引发提前效应而非诱导效应的条件。本研究凸显了超越短期窗口评估强制政策的重要性，并为设计和解释时限性疫苗接种政策提供了分析框架。关键词：强制政策；疫苗接种；激励；接种率；青少年；接种时机；覆盖率。JEL分类：I12；I18。