Limitations
Some of the limitations of our study were that a considerable number of participants dropped out during the study, this study was only performed in one medical center, and that we could not perform genetic sequencing to prove infection with a different clade of the virus, or cultures to prove presence of replication-competent virus. The diagnosis of re-infection in our study is based on RT-PCR results, typical symptoms and the long interval between the two positive results. And, since we did not measure the viral load in patients who tested positive, the diagnosis of re-infection in our study is as certain as is the specificity of the RT-PCR test. We were also unable to perform required serology testing from the beginning of the study.