Asymptomatic SARS-CoV-2 infection in recipients of hematopoietic stem cells in the Omicron period.

Abstract

We aimed to determine the prevalence of SARS-CoV-2 infection, including both symptomatic and asymptomatic courses, and to identify predictors of asymptomatic or symptomatic SARS-CoV-2 infection in patients within seven months after allo-HSCT (allogenic hematopoietic stem cell transplantation) in the Omicron period. Prevalence of the past SARS-CoV-2 infection was determined in patients within seven months after allo-HSCT in the Omicron period using the cellular and humoral immune response against the SARS-CoV-2 nucleoprotein (NCP). Positive markers of past infection were identified in 45.2% of patients (n = 42). The infection was asymptomatic in 68.4% of anti-NCP positive patients. The search for risk factors for symptomatic SARS-CoV-2 infection in allo-HSCT recipients revealed that a low level of B cell reconstitution was the only significantly associated risk factor. A high proportion of allo-HSCT recipients who were asymptomatically infected within up to seven months after transplantation from 2022 to 2023 despite being immunosuppressed and unvaccinated indicates an attenuation of the circulating virus and may signal less risk for transplanted patients from SARS-CoV-2 infection in the Omicron period. Vaccination of these patients against SARS-CoV-2 was shown to be associated with a low but significant risk of exacerbation of cured chronic GVHD (graft versus host disease) and the risk of de novo GVHD. The low level of B-cell reconstitution was the only significant risk factor for symptomatic SARS-CoV-2 infection in HSCT recipients.