Significance of a Known Epidemiological Link to a COVID-19 Index Case and Severity of COVID-19 Infection

ABSTRACT

Background. Several factors have been associated with severity of COVID-19 disease, but there remains a paucity of data surrounding whether the nature of exposure is impactful. Evidence demonstrating the correlation between initial viral exposure dose and disease severity exists for many viral infections. Observational studies have suggested that the exposure context, which can be considered a proxy for magnitude of viral inoculum, may influence severity of COVID-19 infection. We aimed to assess whether having a known exposure, as a proxy for higher inoculum dose to COVID-19, was associated with more severe outcomes for individuals hospitalized with COVID-19. Methods. We created a retrospective cohort of community-dwelling adults hospitalized for COVID-19 in south-central Ontario from April 1, 2020 - January 14, 2021. Individuals or next of kin were contacted to ascertain exposure history. The primary outcome was death, intensive care unit (ICU) admission, or mechanical ventilation (MV) within 30 days of admission. A multivariable logistic regression model was used to determine whether a known exposure was associated with worse outcomes. Results. 1097 individuals with community acquired COVID-19 required hospitalization;of these, 942 (86%) had available exposure data. In this group, the median age was 65, 44% were women, 84% lived in a private residence, 59% had a frailty score (FS) of 1 - 3 while 40% had a FS of 4 - 9, and 28% had a known exposure. Overall, the primary outcome occurred in 368/942 (39%) patients. Having a known exposure was not associated with worse outcome (OR 1.14, 95% CI 0.84-1.54, p = 0.41). Male gender (OR 1.41, 95% CI 1.06-1.89;p = 0.018), age (OR 1.01/year, 95% CI 1.00-1.03, p = 0.03), frailty (OR 1.22/point, 95% CI 1.09-1.36, p = 0.001) and living with at least one other person (OR 1.57, 95% CI 1.09-2.28, p = 0.017) were all associated with death, ICU admission, or MV within 30 days of admission. Conclusion. While having a known exposure to a person with COVID-19 was not associated with worse outcome, the identified increased severity of illness associated with cohabitation suggests context of exposure may have a role in disease severity. This data and future studies can be used to guide public health recommendations to not only minimize transmission, but severity of COVID-19 infection.