[katieHaylor (OP)]

Helen says:

I have heard doctors talk about how much of a virus you can pick up in different situations. Does this mean that the amount of virus you are “dosed” with, so to speak, affects the severity of your illness. If so, how does this work.

What do you think?

[alancalverd]

Viral and bacterial infections are "stochastic" risks.

The probability of infection depends on the quantity of infective particles you are exposed to.

The severity of infection depends on the nature ("quality") of the infective agent and the infected person.

[Petrochemicals]

https://www.thenakedscientists.com/forum/index.php?topic=79084.msg597674#msg597674

[set fair]

The jury is out on this
https://www.sciencedirect.com/science/article/pii/S1201971220304707

[alancalverd]

It's a good attempt at data collection but very weak analysis. Had the only 83-year-old in cluster1 become severe, the entire hypothesis would have been obviously negated!

It is of course possible that a low dose could provoke a sufficient antibody response to confer some degree of  immunity, so there may indeed be a personal threshold. This is the underlying principle of immunisation, after all! But the fact that most of cohort 1 (including the 83-year-old) were wholly asymptomatic points strongly toward a stochastic risk, and the age clustering of  cohort 3 in the "very severe" category suggests that the response is dependent on the victim, not the virus.

If I were on the jury, I'd still be voting for stochastic rather than deterministic risk at this stage.