Purpose: COVID-19 immunity in infected individuals may not be persistent. The specific response wanes in patients who have recovered from this infection. Nevertheless, it has not been fully understood whether true re-infection occurs or the viral reactivation.
Methods: In this study, we investigated three COVID-19 patients who represented the symptoms after recovery. Chest CT scan was applied to assess the patients along with the viral samples from oropharyngeal/nasopharyngeal which were subjected to RT-PCR. The viral genome sequencing was applied where possible to distinguish possible re-infection or latent reactivation. Moreover, COVID-19 specific antibodies available data were evaluated in each incidence.
Results: The second episode of SARS-CoV-2 infection was different among the investigated subjects who experienced an interval between positive PCR tests ranged between 63 and 156 days. The disease presentation was less or more severe in the second infection. All cases were found IgG positive in the re-infection phase. The sequencing of SARS-CoV-2 sample obtained from two cases revealed a D614G mutation of S gene from the second isolated sample strengthens the case for the re-infection.
Conclusions: The possibility of re-infection and reactivation could have significant effect on clinical implications and also vaccination. Our data supports clear warning of SARS-CoV-2 continuous circulation potency among the populations in spite of herd immunity either with natural infection or vaccination. This issue is critical in term of the patients, clinical investigate and viral transmission.