Background Protein-based vaccines for COVID-19 provide a traditional vaccine platform with long-lasting protection for non-SARS-CoV-2 pathogens and may complement messenger RNA vaccines as a booster dose. While NVX-CoV2373 showed substantial early efficacy, the durability of protection has not been delineated. Methods The PREVENT-19 vaccine trial employed a blinded crossover design; the original placebo arm received NVX-CoV2373 after efficacy was established. Using novel statistical methods that integrate surveillance data of circulating strains with post-crossover cases, we estimated placebo-controlled vaccine efficacy and durability of NVX-CoV2373 against both pre-Delta and Delta strains of SARS-CoV-2. Results Vaccine efficacy against pre-Delta strains of COVID-19 was 89% (95% CI: 75%, 95%) and 87% (72%, 94%) at 0 and 90 days after 2 doses of NVX-CoV2373, respectively, with no evidence of waning (p=0.93). Vaccine efficacy against the Delta strain was 88% (71%, 95%), 82% (56%, 92%), and 77% (44%, 90%) at 40, 120, and 180 days, respectively, with evidence of waning (p<0.01). In sensitivity analyses, the estimated Delta vaccine efficacy at 120 days ranged from 66% (15%, 86%) to 89% (74%, 95%) per various assumptions of the surveillance data. Conclusion NVX-CoV2373 has high initial efficacy against pre-Delta and Delta strains of COVID-19 with little evidence of waning for pre-Delta strains through 90 days and moderate waning against Delta strains over 180 days.

中文翻译：

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NVX-CoV2373 疫苗的 Delta 激增对 COVID-19 的持久保护

背景 基于蛋白质的 COVID-19 疫苗为传统的疫苗平台提供了对非 SARS-CoV-2 病原体的持久保护，并且可以作为加强剂量补充信使 RNA 疫苗。虽然 NVX-CoV2373 显示出显着的早期疗效，但保护的持久性尚未确定。方法 PREVENT-19疫苗试验采用盲法交叉设计；最初的安慰剂组在疗效确定后接受了 NVX-CoV2373。使用将流行毒株监测数据与交叉后病例相结合的新颖统计方法，我们评估了 NVX-CoV2373 对 SARS-CoV-2 前 Delta 毒株和 Delta 毒株的安慰剂对照疫苗功效和持久性。结果 接种 2 剂 NVX-CoV2373 后 0 天和 90 天，针对 COVID-19 Delta 前毒株的疫苗功效分别为 89%（95% CI：75%、95%）和 87%（72%、94%） ，没有减弱的证据（p=0.93）。有证据表明，在 40 天、120 天和 180 天时，针对 Delta 菌株的疫苗效力分别为 88%（71%、95%）、82%（56%、92%）和 77%（44%、90%）减弱（p<0.01）。在敏感性分析中，根据监测数据的各种假设，120 天时估计的 Delta 疫苗功效范围为 66%（15%、86%）至 89%（74%、95%）。结论 NVX-CoV2373 对 COVID-19 的 Delta 前菌株和 Delta 菌株具有较高的初始疗效，几乎没有证据表明在 90 天内对 Delta 前菌株的疗效减弱，而在 180 天内对 Delta 菌株的疗效适度减弱。