Fig. 5

Implications of HCoV-exposure- and age-dependent-severity. a A model where disease severity depends only on age (the age-dependent model) is able to explain hospitalisation rates in EU/EEA countries and the UK (dots). Line and filled area represent mean and 95% C.I., respectively. Here, we set a_age = 0.4, b_age = 0.052 years⁻¹ and A₀ = 20 years, after calibrating the model to hospitalisation data in EU/EEA countries and the UK. Results are averaged over 100 samplings from each of 50 different simulations. b Individual risk of developing severe symptoms under exposure-dependent (black) and the age-dependent severity (fuchsia). c, d Severity score distribution within each age class under exposure-dependant and age-dependent severity, respectively. Solid and dashed lines indicate the median score and the 95% percentile range, respectively. Note that c, d have different scales. To estimate individual risk in b, we first selected \( \underset{\_}{N}=3\cdotp {10}^4 \) individuals completely at random in a single simulation (that is, we assume uniform infection rates across all age ranges) and then sampled a fraction π = 0.05 of these \( \underset{\_}{N} \) cases according to the sampling scheme outlined in the “Methods” section. This operation was repeated 2 · 10³ times. Finally, we computed the proportion of high-risk individuals as the fraction of sampled cases whose risk is larger than the 25th percentile in the > 60 years age range. In c, d, the score distribution is computed from a single simulation at the time of the introduction of the pHCoV. We set epidemiological parameters to their baseline values and a = 1.5, b = 0.5, r = 0.05 years⁻¹