Introduction: The duration of immunity after infection from SARS-CoV-2 conferring protection from subsequent COVID-19 episodes is not yet fully understood. We reviewed the literature for cases of documented reinfection.
Materials and methods: A comprehensive computerized search in PubMed, through 15 December 2020, using the following terms in combination: COVID-19, SARS-CoV-2, reinfection, reactivation, recurrence. To exclude cases due to prolonged viral shedding or protracted infection, only cases occurring at least 12 weeks apart or confirmed as being sustained by genetically different viruses by viral genome analysis were included.
Results: We identified 23 cases globally, for which viral genome analysis was performed in 10 cases and serology in 19 cases. The mean interval between the two episodes was 15 weeks. Mean age of cases was 44.5 years, and 10 (43.5%) were women. In 17/23 cases, no comorbidity was observed. In 10 cases, the first episode was more severe than the ensuing episode, whereas in seven cases the ensuing episode was more severe. In four cases, there was no difference in severity and in two cases both episodes were asymptomatic.
Conclusions: From this sample of 23 cases, a clear pattern of the second episode being less or more severe did not emerge. A better understanding of immunity to SARS-CoV-2, necessary to assess the probability of a second infection and the durability of protection conferred by vaccination, is warranted.
Keywords: COVID-19; SARS-CoV-2; immunity; reactivation; recurrence; reinfection; serology.