Refuge in an epidemic, possibly (6,8)

I believe the answer is:

patent medicine

I'm a little stuck... Click here to teach me more about this clue!

'refuge' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps they are linked in a way I don't understand?

'in an epidemic possibly' is the wordplay.
I cannot really see how this works, but
'in' is within the answer.
'an' could be 'i' (Roman numeral for one) and 'i' is found within the answer.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in The Times and The Sunday Times.

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