[C16] Infectious Diseases

[C16-03] Viral shedding and transmissibility in immunocompromised COVID-19 patients: implications for isolation strategies

*Montie Tadaharu Harrison¹, Yong Dam Jeong^1,2, Shingo Iwami¹ (1. Nagoya University (Japan), 2. Pusan National University (Korea))

Keywords:

Immunocompromise,COVID-19,Mathematical modeling,Transmission,Isolation

Immunocompromised individuals infected with SARS-CoV-2 are often reported to experience prolonged viral shedding, increasing their risk of transmitting the virus to susceptible individuals. However, key details regarding viral shedding and transmission in this population remain poorly understood, limiting the ability to inform effective intervention strategies. Here, we analyze the virological and epidemiological characteristics of immunocompromised COVID-19 patients using mathematical modeling and statistical analyses, comparing them to immunocompetent individuals and across varying levels of immunocompromise. Compared to immunocompetent individuals, immunocompromised patients exhibited significant heterogeneity, with higher viral loads at symptom onset and substantially longer viral shedding. While viral load differences at symptom onset between moderately and severely immunocompromised patients were minimal, significantly longer viral shedding durations were observed in the severely immunocompromised patients. Moreover, we found that certain therapeutics such as vaccines and antivirals may have minimal impact on the viral shedding duration in immunocompromised individuals. They were also clustered by their viral shedding durations into shorter and longer shedders. For each group, we estimated the risk of transmission and evaluated the impact of varying isolation durations. Our findings suggest that the current isolation guideline of 20 days after symptom onset for immunocompromised individuals is suitable only for shorter shedders or moderately immunocompromised individuals, and even then, extending isolation by an additional 4 to 5 days may be necessary to effectively reduce the risk of transmission before ending isolation. Finally, we also established a strategy to reliably identify shorter or longer shedders based on viral load measurements obtainable through PCR testing, offering a practical approach to identifying individuals who may require extended isolation durations. Through these results, our study aims to provide insights that inform future pandemic preparedness and intervention strategies for immunocompromised individuals, a high-risk population for infectious diseases.