Wynberg Elke, Lee Sherman, Bavalia Roisin, Eijrond Valerie, Coffeng Luc E, de Vries Anne, van Egmond Saskia, Brals Lobke, Schel Noud A J, Harbers Lotte, Kolen Bas, De Vlas Sake, Schreijer Anja
Pandemic & Disaster Preparedness Center (PDPC), Erasmus MC, Rotterdam, The Netherlands
Mathematical and Economic Modelling Department (MAEMOD), Mahidol Oxford Tropical Medicine Research Unit, Bangkok, Thailand.
BMJ Open. 2025 May 21;15(5):e089610. doi: 10.1136/bmjopen-2024-089610.
Governments used travel bans during the COVID-19 pandemic to limit the introduction of new variant of concern (VoC). In the Netherlands, direct flights from South Africa were banned from 26 November 2021 onwards to curb Omicron (B.1.1.529) importation.
This study retrospectively evaluated the effect of the South African travel ban and the timing of its implementation on subsequent Omicron infections in the Netherlands and, in order to help inform future decision-making, assessed alternative scenarios in which the reproduction number (R) and volume of indirectly imported cases were varied.
Descriptive analysis and modelling study.
Time (days) from 26 November 2021 to reach 10 000 cumulative Omicron infections in the Netherlands.
To benchmark the direct importation rate of Omicron from South Africa, we used the proportion (n/N, %) of passengers arriving on two direct flights from South Africa to the Netherlands on 26 November 2021 with a positive PCR sequencing result for Omicron VoC infection. We scaled the number of directly-imported Omicron infections before and after the travel ban to the incidence in South Africa. We assumed that 10% of all cases continued to arrive via indirect routes, a 'failure rate' of 2% (ie, incoming Dutch citizens not adhering to quarantine on arrival) and an effective reproduction number (R) of Omicron of 1.3. In subsequent analyses, we varied, within plausible limits, the R (1.1-2.0) and proportion of indirectly-imported cases (0-20%).
Compared with no travel ban, the travel ban achieved a 14-day delay in reaching 10 000 Omicron cases, with an additional day of delay if initiated 2 days earlier. If all indirect importation had been prevented (eg, European-wide travel ban), a 21-day delay could have been achieved. The travel ban's effect was negligible if R was ≥2.0 and with a greater volume of ongoing importation.
Travel bans can delay the calendar timing of an outbreak but are substantially less effective for pathogens where importation cannot be fully controlled and tracing every imported case is unfeasible. When facing future disease outbreaks, we urge policy-makers to critically weigh up benefits against the known socioeconomic drawbacks of international travel restrictions.
在新冠疫情期间，各国政府实施旅行禁令以限制新的变异株引入。在荷兰，自2021年11月26日起禁止从南非直飞的航班，以遏制奥密克戎（B.1.1.529）毒株的输入。
本研究回顾性评估了南非旅行禁令及其实施时间对荷兰后续奥密克戎感染的影响，并为辅助未来决策，评估了繁殖数（R）和间接输入病例数变化的替代情景。
描述性分析和建模研究。
从2021年11月26日起至荷兰累计出现10000例奥密克戎感染的时间（天）。
为确定从南非直接输入奥密克戎毒株的速率，我们使用了2021年11月26日乘坐两架从南非直飞荷兰航班的乘客中，奥密克戎变异株感染PCR测序结果呈阳性的比例（n/N，%）。我们根据南非的发病率对旅行禁令前后直接输入的奥密克戎感染病例数进行了调整。我们假设所有病例中有10%继续通过间接途径抵达，“失败率”为2%（即抵达荷兰的本国公民未遵守入境隔离规定），奥密克戎的有效繁殖数（R）为1.3。在后续分析中，我们在合理范围内改变R（1.1 - 2.0）和间接输入病例的比例（0 - 20%）。
与未实施旅行禁令相比，旅行禁令使达到10000例奥密克戎病例的时间延迟了14天，如果提前2天实施，延迟时间会增加1天。如果完全防止了所有间接输入（例如全欧洲范围的旅行禁令），则可以实现21天的延迟。如果R≥2.0且持续输入量较大，旅行禁令的效果可忽略不计。
旅行禁令可以推迟疫情爆发的时间，但对于无法完全控制输入且追踪每一例输入病例不可行的病原体，其效果要差得多。面对未来的疾病爆发，我们敦促政策制定者认真权衡国际旅行限制已知的社会经济弊端与其带来的益处。
