Faculty of Biology, Technion - Israel Institute of Technology, Haifa, Israel.
Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel.
Nat Med. 2021 Dec;27(12):2108-2110. doi: 10.1038/s41591-021-01575-4. Epub 2021 Nov 2.
The effectiveness of the coronavirus disease 2019 (COVID-19) BNT162b2 vaccine in preventing disease and reducing viral loads of breakthrough infections (BTIs) has been decreasing, concomitantly with the rise of the Delta variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, it is unclear whether the observed decreased effectiveness of the vaccine in reducing viral loads is inherent to the Delta variant or is dependent on time from immunization. By analyzing viral loads of over 16,000 infections during the current, Delta-variant-dominated pandemic wave in Israel, we found that BTIs in recently fully vaccinated individuals have lower viral loads than infections in unvaccinated individuals. However, this effect starts to decline 2 months after vaccination and ultimately vanishes 6 months or longer after vaccination. Notably, we found that the effect of BNT162b2 on reducing BTI viral loads is restored after a booster dose. These results suggest that BNT162b2 might decrease the infectiousness of BTIs even with the Delta variant, and that, although this protective effect declines with time, it can be restored, at least temporarily, with a third, booster, vaccine dose.
新型冠状病毒病 2019（COVID-19）疫苗 BNT162b2 在预防疾病和降低突破性感染（BTIs）的病毒载量方面的有效性一直在下降，同时严重急性呼吸综合征冠状病毒 2（SARS-CoV-2）的 Delta 变体也在上升。然而，目前尚不清楚观察到的疫苗降低病毒载量的效果是否是 Delta 变体固有的，还是取决于接种疫苗后的时间。通过分析当前在以色列 Delta 变体主导的大流行浪潮中超过 16000 例感染的病毒载量，我们发现最近完全接种疫苗的个体中的 BTIs 的病毒载量低于未接种疫苗的个体中的感染。然而，这种效果在接种疫苗后 2 个月开始下降，并且在接种疫苗 6 个月或更长时间后最终消失。值得注意的是，我们发现 BNT162b2 对降低 BTI 病毒载量的作用在加强剂量后得到恢复。这些结果表明，即使存在 Delta 变体，BNT162b2 也可能降低 BTIs 的传染性，并且尽管这种保护作用随时间下降，但可以通过第三剂、加强剂疫苗剂量至少暂时恢复。
