This paper estimates the outcomes of two different COVID-19 vaccination strategies in Canada for the mRNA vaccines currently approved for Emergency Use Authorization (EUA), modelled on the vaccination and effectiveness of the Pfizer vaccine which is likely to be more widely administered in Canada. The first strategy is the manufacturer recommended standard of two doses (two-dose strategy) given within 21 days apart versus a strategy of giving a larger group a single dose of vaccine (first-dose-for-most strategy) by delaying the second injection. Three parameters are varied in the course of 36 estimation scenarios of the population-level effects of the two vaccination strategies. The first is the effectiveness of a single dose of vaccine at preventing disease, the second is the effectiveness of the vaccine at preventing transmission of the virus, and the third is the rate of transmission of the virus during the course of the simulations. Over the course of the different scenarios, the first-dose-for-most strategy was superior in reducing disease transmission in all scenarios where vaccination is assumed to have an effect on viral transmission. The results for fatalities was mixed, with the first-dose-for-most strategy being superior in cases where a higher first-dose effectiveness at preventing disease was assumed. Finally, in the best-guess scenarios where a 75% reduction in disease transmission and a 92.6% effectiveness at preventing disease from a single dose were used, the first-dose-for-most strategy was superior in a situation with reduced vaccine doses available, and switching to the first-dose-for-most strategy earlier helped to prevent a higher proportion of cases and deaths.

中文翻译：

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不同假设下加拿大的疫苗接种策略比较

本文以辉瑞疫苗的疫苗接种和有效性为模型，评估了加拿大目前批准用于紧急使用授权（EUA）的mRNA疫苗的两种不同的COVID-19疫苗接种策略的结果，该疫苗可能在加拿大得到更广泛的应用。第一种策略是制造商建议的间隔21天之内两次注射的标准剂量（两次剂量策略），而不是通过延迟第二次注射为更大的群体提供单剂量疫苗的策略（多数剂量第一剂策略） 。在对两种疫苗接种策略的人口水平影响的36个估计方案的过程中，三个参数有所不同。首先是单剂疫苗在预防疾病方面的有效性，其次是疫苗在预防病毒传播方面的有效性，第三是模拟过程中病毒的传播速率。在不同的情况下，假定疫苗接种对病毒传播有影响的所有情况下，“最先给药”策略在减少疾病传播方面均具有优势。致死率的结果好坏参半，如果假定较高的预防疾病有效剂量的情况下，“最先给药”策略是更好的选择。最后，在最佳猜测的情况下，使用单剂量减少75％的疾病传播和92.6％的预防疾病有效性，在减少可用疫苗剂量的情况下，“最先剂量”策略是更好的，并且较早采用“首剂为一”的策略有助于防止更多的病例和死亡。