A five-compartment model of age-specific transmissibility of SARS-CoV-2

BACKGROUND: The novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, also called 2019-nCoV) causes different morbidity risks to individuals in different age groups. This study attempts to quantify the age-specific transmissibility using a mathematical model. METHODS: An epidemiological model with five compartments (susceptible–exposed–symptomatic–asymptomatic–recovered/removed [SEIAR]) was developed based on observed transmission features. Coronavirus disease 2019 (COVID-19) cases were divided into four age groups: group 1, those ≤ 14 years old; group 2, those 15 to 44 years old; group 3, those 45 to 64 years old; and group 4, those ≥ 65 years old. The model was initially based on cases (including imported cases and secondary cases) collected in Hunan Province from January 5 to February 19, 2020. Another dataset, from Jilin Province, was used to test the model. RESULTS: The age-specific SEIAR model fitted the data well in each age group (P < 0.001). In Hunan Province, the highest transmissibility was from age group 4 to 3 (median: β(43) = 7.71 × 10(− 9); SAR(43) = 3.86 × 10(− 8)), followed by group 3 to 4 (median: β(34) = 3.07 × 10(− 9); SAR(34) = 1.53 × 10(− 8)), group 2 to 2 (median: β(22) = 1.24 × 10(− 9); SAR(22) = 6.21 × 10(− 9)), and group 3 to 1 (median: β(31) = 4.10 × 10(− 10); SAR(31) = 2.08 × 10(− 9)). The lowest transmissibility was from age group 3 to 3 (median: β(33) = 1.64 × 10(− 19); SAR(33) = 8.19 × 10(− 19)), followed by group 4 to 4 (median: β(44) = 3.66 × 10(− 17); SAR(44) = 1.83 × 10(− 16)), group 3 to 2 (median: β(32) = 1.21 × 10(− 16); SAR(32) = 6.06 × 10(− 16)), and group 1 to 4 (median: β(14) = 7.20 × 10(− 14); SAR(14) = 3.60 × 10(− 13)). In Jilin Province, the highest transmissibility occurred from age group 4 to 4 (median: β(43) = 4.27 × 10(− 8); SAR(43) = 2.13 × 10(− 7)), followed by group 3 to 4 (median: β(34) = 1.81 × 10(− 8); SAR(34) = 9.03 × 10(− 8)). CONCLUSIONS: SARS-CoV-2 exhibits high transmissibility between middle-aged (45 to 64 years old) and elderly (≥ 65 years old) people. Children (≤ 14 years old) have very low susceptibility to COVID-19. This study will improve our understanding of the transmission feature of SARS-CoV-2 in different age groups and suggest the most prevention measures should be applied to middle-aged and elderly people.