Telethon Kids Institute, Nedlands, WA, Australia; Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, VIC, Australia.
Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, VIC, Australia.
Epidemics. 2024 Jun;47:100763. doi: 10.1016/j.epidem.2024.100763. Epub 2024 Mar 19.
The availability of COVID-19 vaccines promised a reduction in the severity of disease and relief from the strict public health and social measures (PHSMs) imposed in many countries to limit spread and burden of COVID-19. We were asked to define vaccine coverage thresholds for Australia's transition to easing restrictions and reopening international borders. Using evidence of vaccine effectiveness against the then-circulating Delta variant, we used a mathematical model to determine coverage targets. The absence of any COVID-19 infections in many sub-national jurisdictions in Australia posed particular methodological challenges. We used a novel metric called Transmission Potential (TP) as a proxy measure of the population-level effective reproduction number. We estimated TP of the Delta variant under a range of PHSMs, test-trace-isolate-quarantine (TTIQ) efficiencies, vaccination coverage thresholds, and age-based vaccine allocation strategies. We found that high coverage across all ages (≥70%) combined with ongoing TTIQ and minimal PHSMs was sufficient to avoid lockdowns. At lesser coverage (≤60%) rapid case escalation risked overwhelming of the health sector or the need to reimpose stricter restrictions. Maintaining low case numbers was most beneficial for health and the economy, and at higher coverage levels (≥80%) further easing of restrictions was deemed possible. These results directly informed easing of COVID-19 restrictions in Australia.
COVID-19 疫苗的问世有望减轻疾病的严重程度，并缓解许多国家为限制 COVID-19 的传播和负担而实施的严格公共卫生和社会措施（PHSMs）。我们被要求为澳大利亚放宽限制和重新开放国际边界的过渡定义疫苗接种覆盖率的门槛。我们使用针对当时流行的 Delta 变体的疫苗有效性证据，使用数学模型来确定覆盖目标。澳大利亚许多次国家司法管辖区没有任何 COVID-19 感染，这给我们带来了特殊的方法学挑战。我们使用了一种称为传播潜力（TP）的新指标作为人群有效繁殖数的代理指标。我们根据一系列 PHSMs、测试-追踪-隔离-检疫（TTIQ）效率、疫苗接种覆盖率门槛以及基于年龄的疫苗分配策略，估计了 Delta 变体的 TP。我们发现，所有年龄段的高覆盖率（≥70%）加上持续的 TTIQ 和最小的 PHSMs 足以避免封锁。在覆盖率较低（≤60%）的情况下，病例快速升级可能会使卫生部门不堪重负，或需要重新实施更严格的限制。保持低病例数对健康和经济最有益，在较高的覆盖率水平（≥80%）下，进一步放宽限制被认为是可能的。这些结果直接为澳大利亚放宽 COVID-19 限制提供了信息。
