Authors: To et al., 2020
Journal: Clinical Infectious Diseases
Tags: immunity, reinfection
Summary: This study intended to distinguish re-infection from prolonged viral shedding of SARS-CoV-2 using whole genome sequencing. The researchers evaluated a 33-year old male patient experiencing a second episode of infection four months (142 days) after his first symptomatic episode. The patient was asymptomatic during the second episode after returning to Hong Kong from a trip to Spain via United Kingdom. Genomic analysis was conducted on the samples from each episode to differentiate re-infection from persistent shedding. Viral genomes from the first and second episodes belonged to different clades (i.e., lineage). Viral genomes were compared using the international GISAID database to determine genomic relatives. The viral genome from the first episode was most related to strains from the United States or England collected in March and April; the second was most closely related to strains from Switzerland and England collected in July and August. This study suggests that re-infection of SARS-CoV-2 is possible with different phylogenetic strains. In this case, the second infection was milder than the previous.
Limitations: This is a report of a single individual. The role of long-term immunity is difficult to interpret from this study due to limited serological evidence during the first episode: the only sample taken during the first episode was within 10 days of onset and was negative for IgG antibodies, and antibody response may not mount until 10 or more days post-infection. This patient did develop detectable IgG after the second infection when tested at day 5 after an asymptomatic positive test.