So if the model is true, one potential source of temporal variation might be waning immunity acquired after being exposed but not infected. Will link studies later, but many non-infected people show some T-cell responses against Sars-Cov2. In this scenario, e.g. a doctor gets coughed on, gets lucky, and develops some sort of temporal immunity that protects them for the next few months. After some time though this protection wanes and their risk increases again (this would probably not be a binary but continuous process).
I know too little about immunology, but afaik T-cell immunity wanes very slowly, so it does not quite fit the mark. Maybe there are other forms of immunity/antibodies that would explain this better.
It does seem that close contacts of infected people acquire T-cell immunity even without infection, but at least 90 days after exposure there does not seem to be a decreasing trend: https://www.nature.com/articles/s41467-021-22036-z
So if the model is true, one potential source of temporal variation might be waning immunity acquired after being exposed but not infected. Will link studies later, but many non-infected people show some T-cell responses against Sars-Cov2. In this scenario, e.g. a doctor gets coughed on, gets lucky, and develops some sort of temporal immunity that protects them for the next few months. After some time though this protection wanes and their risk increases again (this would probably not be a binary but continuous process).
I know too little about immunology, but afaik T-cell immunity wanes very slowly, so it does not quite fit the mark. Maybe there are other forms of immunity/antibodies that would explain this better.
It does seem that close contacts of infected people acquire T-cell immunity even without infection, but at least 90 days after exposure there does not seem to be a decreasing trend: https://www.nature.com/articles/s41467-021-22036-z