Fig. 3.

Changes in age-specific seroprevalence under different assumptions on antibody boosting and the relative infectivity of children. (A) Changes in seroprevalence calculated using the titre model with full parameter sets (model A) from the first day of the pandemic until the follow-up recruiting time T2. Blue, the titre model with pre-existing immunity in the elderly set to twice that of other age groups (default setting). Red, the titre model with reduced pre-existing immunity in the elderly and all age groups have the same seroprevalence. Green, the titre model with higher pre-existing immunity in the elderly set to 4 times that of other age groups. (B) Changes of the seroprevalence calculated using the titre model with the same antibody boosting among different age groups (model B). Colours are the same as in (A). (C) Changes of the seroprevalence calculated, using the titre model without the increased relative infectivity of children (model C). Colours are the same as in (A). Note that the changes in seroprevalence in model C were measured from the first day of the pandemic until the follow-up recruiting time T2 plus additional 60 days to adjust for the delay of the peak. Similar patterns of seroprevalence were able to be produced if T2 was used instead of T2 plus 60 days. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of the article.)