In the context of Covid-19, in Denmark all ferrets/minks in farms were killed, as there is infection in humans by the ferret corona-subtype.

Contrary heightened concerns, a virus transferred from ferret might be less dangerous than its human subtype that is transmitted within humans. That is my inference from Jenner introducing vaccination (vacca means cow): pox virus from cow is not as dangerous to humans as the human small pox virus, in spite of its strong effect of immunization against the latter. In other words, it seems possible that the true principle of vaccination is cross reactivity and not attenuation. To attenuate one and the same antigen that causes the disease seems different from "being lucky" (compare comments, this is an edited version of my question) as Jenner is considered to have been when using antigen A as a cross-reactive antigen instead an attenuated identical antigen.

Is the following reasoning coheherent? The general principle of vaccination is cross-reactivity, not attenuation, as even in case of apparently identical antigen used after attenuation there is a broad specifity of anti-body reaction that - this is important and new, in this edited version of my question - "of course" is more specific that Jenner's vaccine as it indeed is one and the same antigen - however, attenuation must be seen in reference to a very narrow specifity of target cells, i.e. non-immune cells, that Jenner's dosis just did not reach as he was using a cross-reactive vaccine of a different species of virus the cross-reactivity of which was effective against in that case small pox, not cow pox. So, is the underlying principle of vaccination not attenuation and identity of antigens but attenuation and - on the other hand - very narrow specifity of target cells, that Jenner's vaccine gladly was not able to surmount?

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    $\begingroup$ You're talking about completely different things, and it's not at all clear (especially after reading your self-answer) that you have any idea what you're talking about. Vaccinia and variola are two entirely separate species, while both the mink and human SARS-CoV-2 viruses are just different subtypes of the same virus. Just because Vaccinia (usually) causes a sub-lethal and eventually protective infection in humans doesn't mean anything of the sort is going on with the mink and human SARS-CoV-2 variants. Jenner was extremely lucky. $\endgroup$
    – MattDMo
    Nov 11 '20 at 18:09
  • $\begingroup$ "self-answer" is pejorative for "jeopardy question and answer style share your wisdom - did I choose the wrong form, it's encouraged to answer your own question. $\endgroup$ Nov 13 '20 at 8:28
  • $\begingroup$ To MatDMO: what you're explaining contentwise suits me well That's my very question, if vaccinia virus and variola virus are or are not different in respect of immunity, and to what extent exactly. as they quite strikingly induce "cross-reactive" immunity! If you only told me what exactly the difference is between variola and vaccinia is that could be the start of a great affinity (of ours, smile).However, "Jenner was just lucky" does in fact answer my question, in the negative and according to common wisdom and perspective. $\endgroup$ Nov 13 '20 at 8:32
  • $\begingroup$ Hint: to reply to someone's comment, simply use the @username convention. I would be @MattDMo, for instance. As you type, an autocomplete box will pop up, so you don't have to type out the whole thing. The reason I'm not pinging you in this comment is because you are the original poster (OP), and so are notified of all comments in this area. In comments under answers. you would be pinged if someone @ mentions you. $\endgroup$
    – MattDMo
    Nov 13 '20 at 17:49
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    $\begingroup$ Changing a question completely by editing after it was answered it seen as bad practice, as this also does not respect the work of the answer. Please stop this. I will rollback the edits and lock the post. $\endgroup$
    – Chris
    Feb 1 at 19:19

We cannot say if the virus in ferrets gets less or more dangerous than the one which actually circulates in humans. There are two problems with this infection:

  • The ferrets can build a reservoir for the virus making it possible for circulation to occur among these animals and re-introduce it into the human population. It may also be possible that the virus jumps into other animals, also enabling transmission.
  • It is possible that the virus mutates in the animals (it does this anyways) and changes, so acquired immunity against the original SARS-CoV-2 it will not be present or at least less effective, enabling further infections. This can also render a vaccine directed against a mutated part ineffective.

So far, these things are concerns only, but to avoid them, swift action with the killing of all Danish ferrets has been taken.

About your example with Jenner: He was simply lucky that the cow pox he used for this experiment where close enough to the small pox to generate immunity. For the SARS virus we still talk about the same virus, not a different one.


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