By Kåre Mølbak et al.
Source Frontiers
Introduction
During the COVID-19 pandemic, much has been said about the importance of host-specific and virus-specific factors as predictors of the risk of infection and severity of disease. For example, host factors such as increased age, male gender, ethnicity, and comorbidities such as metabolic and pulmonary disorders have been recognized as risk factors for severe disease, whereas host immunity stemming from prior infection or vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is associated with reduced severity. Similarly, the viral evolution of SARS-CoV-2 over the past 4 years has been scrutinized to estimate changes in the relative transmissibility, virulence and vaccine-match of each emerging variant over time during the COVID-19 pandemic. However, despite this scrutiny, variation in transmissibility and severity of disease remain imperfectly understood.
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