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The letter to the editor discusses a study conducted in South Korea that examined the immune response to COVID-19 in healthcare workers. The study found that individuals with hybrid immunity, meaning they had both natural infection and vaccination, and higher levels of certain antibodies had a lower risk of subsequent infection. The study suggests that these antibody levels can be used as an indicator of protection against infection. However, baseline saliva IgA antibodies did not show a protective role. The study concludes that further research is needed to fully understand the mechanisms involved. [Extracted from the article]

There are limited data supporting current Centers for Disease Control and Prevention guidelines for the isolation period in moderate to severely immunocompromised patients with coronavirus disease 2019 (COVID‐19). Adult COVID‐19 patients who underwent solid organ transplantation (SOT) or received active chemotherapy against hematologic malignancy were enrolled and weekly respiratory samples were collected. Samples with positive genomic real‐time polymerase chain reaction results underwent virus culture and rapid antigen testing (RAT). A total of 65 patients (40 with hematologic malignancy and 25 SOT) were enrolled. The median duration of viable virus shedding was 4 weeks (interquartile range: 3–7). Multivariable analysis revealed that B‐cell depletion (hazard ratio [HR]: 4.76) was associated with prolonged viral shedding, and COVID‐19 vaccination (≥3 doses) was negatively associated with prolonged viral shedding (HR: 0.22). The sensitivity, specificity, positive predictive value, and negative predictive value of RAT for viable virus shedding were 79%, 76%, 74%, and 81%, respectively. The negative predictive value of RAT was only 48% (95% confidence interval [CI]: 33–65) in the samples from those with symptom onset ≤20 days, but it was as high as 92% (95% CI: 85–96) in the samples from those with symptom onset >20 days. About half of immunocompromised COVID‐19 patients shed viable virus for ≥4 weeks from the diagnosis, and virus shedding was prolonged especially in unvaccinated patients with B‐cell‐depleting therapy treatment. RAT beyond 20 days in immunocompromised patients had a relatively high negative predictive value for viable virus shedding. [ABSTRACT FROM AUTHOR]

This article explores the use of whole genome sequencing (WGS) to analyze the mutations of the SARS-CoV-2 virus in immunocompromised patients with persistent viral detection. The study, conducted at a tertiary teaching hospital, included 13 patients and found that each patient had unique and different mutations distributed throughout the entire SARS-CoV-2 genome. These findings suggest that immunocompromised patients may contribute to the emergence of new variants. The study focused on mutations during the Omicron era and found that patients acquired a median of two amino acid substitutions over a median of 51 days, with most mutations occurring in specific regions of the genome. Some mutations were associated with immune evasion, remdesivir resistance, and the emergence of new variants. The study suggests that immunocompromised individuals with persistent viral detection should be cautious about ending isolation, but the results may not apply to all immunocompromised populations due to limitations in the study. [Extracted from the article]