  Several important aspects related to SARS-CoV-2 transmission are not well
known due to a lack of appropriate data. However, mathematical and
computational tools can be used to extract part of this information from the
available data, like some hidden age-related characteristics. In this paper, we
present a method to investigate age-specific differences in transmission
parameters related to susceptibility to and infectiousness upon contracting
SARS-CoV-2 infection. More specifically, we use panel-based social contact data
from diary-based surveys conducted in Belgium combined with the next generation
principle to infer the relative incidence and we compare this to real-life
incidence data. Comparing these two allows for the estimation of age-specific
transmission parameters. Our analysis implies the susceptibility in children to
be around half of the susceptibility in adults, and even lower for very young
children (preschooler). However, the probability of adults and the elderly to
contract the infection is decreasing throughout the vaccination campaign,
thereby modifying the picture over time.
