Emerg Infect Dis. 2023 Oct;29(10):1999-2007. doi: 10.3201/eid2910.230055. Epub 2023 Aug 28.
In British Columbia, Canada, initial growth of the SARS-CoV-2 Delta variant was slower than that reported in other jurisdictions. Delta became the dominant variant (>50% prevalence) within ≈7-13 weeks of first detection in regions within the United Kingdom and United States. In British Columbia, it remained at <10% of weekly incident COVID-19 cases for 13 weeks after first detection on March 21, 2021, eventually reaching dominance after 17 weeks. We describe the growth of Delta variant cases in British Columbia during March 1-June 30, 2021, and apply retrospective counterfactual modeling to examine factors for the initially low COVID-19 case rate after Delta introduction, such as vaccination coverage and nonpharmaceutical interventions. Growth of COVID-19 cases in the first 3 months after Delta emergence was likely limited in British Columbia because additional nonpharmaceutical interventions were implemented to reduce levels of contact at the end of March 2021, soon after variant emergence.
在加拿大不列颠哥伦比亚省，SARS-CoV-2 德尔塔变异株的初始增长率低于其他司法管辖区的报告。德尔塔变异株在英国和美国的部分地区首次检测到后的 ≈7-13 周内成为主要变异株（>50%的流行率）。在不列颠哥伦比亚省，自 2021 年 3 月 21 日首次发现以来的 13 周内，其每周 COVID-19 病例的占比一直低于 10%，最终在 17 周后占据主导地位。我们描述了 2021 年 3 月 1 日至 6 月 30 日期间不列颠哥伦比亚省德尔塔变异株病例的增长情况，并应用回溯性对照模型来研究德尔塔变异株引入后 COVID-19 病例率初始较低的因素，如疫苗接种覆盖率和非药物干预措施。在德尔塔变异株出现后的头 3 个月，不列颠哥伦比亚省的 COVID-19 病例增长可能受到限制，因为在变异株出现后不久的 2021 年 3 月底，又实施了额外的非药物干预措施来降低接触水平。
