Department of Genetics, Stanford University, Stanford, CA, United States of America.
Premier Research, Morrisville, NC, United States of America.
PLoS One. 2022 Sep 9;17(9):e0274509. doi: 10.1371/journal.pone.0274509. eCollection 2022.
The COVID-19 pandemic has had a devastating impact on the world over the past two years (2020-2021). One of the key questions about its future trajectory is the protection from subsequent infections and disease conferred by a previous infection, as the SARS-CoV-2 virus belongs to the coronaviruses, a group of viruses the members of which are known for their ability to reinfect convalescent individuals. Bulgaria, with high rates of previous infections combined with low vaccination rates and an elderly population, presents a somewhat unique context to study this question.
We use detailed governmental data on registered COVID-19 cases to evaluate the incidence and outcomes of COVID-19 reinfections in Bulgaria in the period between March 2020 and early December 2021.
For the period analyzed, a total of 4,106 cases of individuals infected more than once were observed, including 31 cases of three infections and one of four infections. The number of reinfections increased dramatically during the Delta variant-driven wave of the pandemic towards the end of 2021. We observe a moderate reduction of severe outcomes (hospitalization and death) in reinfections relative to primary infections, and a more substantial reduction of severe outcomes in breakthrough infections in vaccinated individuals.
In the available datasets from Bulgaria, prior infection appears to provide some protection from severe outcomes, but to a lower degree than the reduction in severity of breakthrough infections in the vaccinated compared to primary infections in the unvaccinated.
在过去的两年（2020-2021 年）中，COVID-19 大流行对世界造成了毁灭性的影响。关于其未来轨迹的一个关键问题是先前感染所带来的对后续感染和疾病的保护，因为 SARS-CoV-2 病毒属于冠状病毒，这一组病毒的成员以能够使康复个体再次感染而闻名。保加利亚先前感染率高，疫苗接种率低，人口老龄化，为研究这一问题提供了一个略显独特的背景。
我们使用关于登记的 COVID-19 病例的详细政府数据，评估 2020 年 3 月至 2021 年 12 月初期间保加利亚 COVID-19 再感染的发病率和结果。
在所分析的时间段内，共观察到 4106 例个体多次感染的病例，包括 31 例三次感染和一例四次感染。在 2021 年末，Delta 变体驱动的大流行浪潮期间，再感染的数量急剧增加。我们观察到再感染的严重后果（住院和死亡）相对于初次感染有所减轻，而在接种疫苗的个体中，突破性感染的严重后果减轻更为显著。
在保加利亚的现有数据集，先前的感染似乎提供了对严重后果的一定保护，但与未接种疫苗的突破性感染相比，接种疫苗的个体的严重后果减轻程度要低。
