Background

At interim analysis in a phase 3, observer-blinded, placebo-controlled clinical trial, the mRNA-1273 vaccine showed 94.1% efficacy in preventing coronavirus disease 2019 (Covid-19). After emergency use of the vaccine was authorized, the protocol was amended to include an open-label phase. Final analyses of efficacy and safety data from the blinded phase of the trial are reported.

Methods

We enrolled volunteers who were at high risk for Covid-19 or its complications; participants were randomly assigned in a 1:1 ratio to receive two intramuscular injections of mRNA-1273 (100 μg) or placebo, 28 days apart, at 99 centers across the United States. The primary end point was prevention of Covid-19 illness with onset at least 14 days after the second injection in participants who had not previously been infected with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The data cutoff date was March 26, 2021.

Results

The trial enrolled 30,415 participants; 15,209 were assigned to receive the mRNA-1273 vaccine, and 15,206 to receive placebo. More than 96% of participants received both injections, 2.3% had evidence of SARS-CoV-2 infection at baseline, and the median follow-up was 5.3 months in the blinded phase. Vaccine efficacy in preventing Covid-19 illness was 93.2% (95% confidence interval [CI], 91.0 to 94.8), with 55 confirmed cases in the mRNA-1273 group (9.6 per 1000 person-years; 95% CI, 7.2 to 12.5) and 744 in the placebo group (136.6 per 1000 person-years; 95% CI, 127.0 to 146.8). The efficacy in preventing severe disease was 98.2% (95% CI, 92.8 to 99.6), with 2 cases in the mRNA-1273 group and 106 in the placebo group, and the efficacy in preventing asymptomatic infection starting 14 days after the second injection was 63.0% (95% CI, 56.6 to 68.5), with 214 cases in the mRNA-1273 group and 498 in the placebo group. Vaccine efficacy was consistent across ethnic and racial groups, age groups, and participants with coexisting conditions. No safety concerns were identified.

Conclusions

The mRNA-1273 vaccine continued to be efficacious in preventing Covid-19 illness and severe disease at more than 5 months, with an acceptable safety profile, and protection against asymptomatic infection was observed. (Funded by the Biomedical Advanced Research and Development Authority and the National Institute of Allergy and Infectious Diseases; COVE ClinicalTrials.gov number, NCT04470427.)

中文翻译：

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mRNA-1273 SARS-CoV-2 疫苗在盲法阶段完成后的功效

背景

在一项观察者盲法、安慰剂对照的 3 期临床试验的中期分析中，mRNA-1273 疫苗在预防 2019 年冠状病毒病 (Covid-19) 方面显示出 94.1% 的功效。在授权紧急使用疫苗后，方案进行了修改，纳入了开放标签阶段。报告了试验盲态阶段的有效性和安全性数据的最终分析。

方法

我们招募了感染 Covid-19 或其并发症的高风险志愿者；参与者以 1:1 的比例随机分配，在美国 99 个中心接受两次 mRNA-1273（100 μg）或安慰剂肌肉注射，间隔 28 天。主要终点是预防先前未感染过严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) 的参与者在第二次注射后至少 14 天发病的 Covid-19 疾病。数据截止日期为2021年3月26日。

结果

该试验招募了 30,415 名参与者；15,209 人被分配接受 mRNA-1273 疫苗，15,206 人被分配接受安慰剂。超过 96% 的参与者接受了两次注射，2.3% 的参与者在基线时有 SARS-CoV-2 感染的证据，盲法阶段的中位随访时间为 5.3 个月。疫苗预防 Covid-19 疾病的功效为 93.2%（95% 置信区间 [CI]，91.0 至 94.8），mRNA-1273 组有 55 例确诊病例（每 1000 人年 9.6 例；95% CI，7.2 至 12.5） ）和安慰剂组 744 例（每 1000 人年 136.6 例；95% CI，127.0 至 146.8）。预防重症的有效率为98.2%（95% CI，92.8～99.6），mRNA-1273组有2例，安慰剂组有106例，第二次注射后14天开始预防无症状感染的有效率是63.0％（95％CI，56.6至68.5），mRNA-1273组有214例，安慰剂组有498例。疫苗功效在民族和种族群体、年龄组以及患有共存疾病的参与者中是一致的。没有发现任何安全问题。

结论

mRNA-1273疫苗在5个多月内持续有效预防Covid-19疾病和严重疾病，具有可接受的安全性，并且观察到对无症状感染的保护作用。（由生物医学高级研究与开发局和国家过敏和传染病研究所资助；COVE ClinicalTrials.gov 编号，NCT04470427。）