Viral infectivity in pediatric SARS-CoV-2 clinical samples does not vary by age

Abstract

During the early months of the SARS-CoV-2 pandemic, notable uncertainty emerged regarding the role of children in transmission dynamics. With time, it became more clear that children were susceptible to infection with SARS-CoV-2, but that the vast majority of children experienced mild symptoms with lower incidence of severe disease. This pattern remained consistent despite the later emergence of SARS-CoV-2 variants, including Delta and Omicron, even among children <5 ineligible for vaccination. The relative lack of severe disease in the pediatric population raised questions regarding viral kinetics and infectivity in children versus adults. We hypothesized that unique virologic features in children could explain this apparent decrease in symptoms and transmissibility early in the pandemic.

Figure 1.. SARS-CoV-2 viral infectivity does not vary by age in a pediatric population.

A set of 144 clinical samples from children infected with SARS-CoV-2 was used to examine the relationship between infectious virus titer and RNA viral load as a function of patient age. Individual specimen measurements of E gene RNA levels (C_T) on the x-axis are plotted against viral titer, as measured in focus forming units (FFU/mL) on the y-axis. Dashed line indicates the limit of detection for infectious titer (20 FFU/mL). Samples for which we could not measure a viral titer were assigned fixed values of one-tenth the limit of detection (2 FFU/mL). Lines of best fit were generated by linear regression on log-transformed titer data as a function of C_T and age group.