“Methods: For this systematic review, we searched scientific publications on PubMed and, the pre-print server, MedRxiv through August 18, 2021…
To identify relevant studies with appropriate control groups, we developed the following criteria for studies to be included in the systematic analysis: (1) baseline polymerase chain reaction (PCR) testing, (2) a negative comparison group, (3) longitudinal follow-up, (4) a cohort of human participants, i.e., not a case report or case series, and (5) outcome determined by PCR.
The review was conducted following PRISMA guidelines. We assessed for selection, information, and analysis bias, per PRISMA guidelines.
The review was conducted following PRISMA guidelines.
Results: We identified 1,392 reports. Of those reports, 10 studies met the study inclusion criteria from 6 different countries. The total population in the 10 studies included 9,930,470 individuals with a median observation period that ranged from one to 10.3 months.
We found that the relative decreased risk of SARS-CoV-2 reinfection ranged between 80.5 to 100% compared to those without prior infection (See table 1 below). The weighted average risk reduction against reinfection was 90.4%, with a standard deviation of 7.7%. The p-value for percentage reduction was less than 0.01..”
