Sean, a vaccine is made partially from a virus, so Confederate’s question is important.  
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Honestly, we need a good, orthodox, Catholic virologist to answer these scientific concerns.    

As far as I can tell, CC is suggesting the virus will change over time, thereby making the indirect voluntary act of using abortive vaccines less culpable (ie., more remote cooperation in evil than for those using the previous rendition).

But I am saying that is irrelevant:

The HEK293 remains unchanged, regardless of how many mutations the virus undergoes.
PS: This logic is faulty anyway, as it would conclude that using abortive fetal cells in vaccines from the 1972 abortion is more remote (therefore less culpable) than using vaccines developed with the aid of aborted fetal matter from the 1985 aborted foetus.

Yes it does

If the 1st replication contained 98% of the original material and 20th contained 50% and the 95th contained 20% and the 200th contained 0% then yes this is the case. Virus use the genetic material available to replicate it changes everytime it makes a copy since it is in a new host

Even if it were true that none of the COVID19 vaccines were developed using HEK293 (which it is not), the entire discussion of remote/indirect cooperation in evil in this context is subterfuge:

The cooperation is direct, as Fr./Dr. Peter Scott stated:

“However, the vaccine is not just an indirect effect of the abortion.  There is, in fact, a direct line of causality from the abortion to the available fetal cells, to the development of the vaccine, to the immunization.  Therefore, the immunization is a direct consequence of the abortion, and not just an indirect effect.”

The greater or lesser “remoteness” is irrelevant.

No it's not. Again if no original material exists this is not the case.
The argument that you wish to make is simple and valid if worded as 'the usage of any portion of an aborted child is repugnant" end of story end of argument.

This however is not the way some see this and denying the usage of a thing is based upon principals of Medico-Moral teaching. Most are not equipped to do so, this the Church set up institutes to answer the questions.

You can not pretend that a simple knowledge of Moral theology suffices,

Fr. Scott is also a medical doctor.

Additionally, none of the prelates (Vigano, Burke, Schneider, Strickland, et al) are seeing this issue from your perspective.  They are all saying we can never use vaccines which used abortive fetal matter at any stage of their development.

That is a rejection of the remoteness argument you are making, and a complete disregard for how much HEK293 is in today’s vaccines.

Ps: Not that it matters, but you also never proved your contention that today’s vaccines contain no HEK293.  You simply made the assertion.

With respect, Sean, I believe that Fr Scott was a medicine student at one point in his life, but did not complete the training. Not that that disqualifies him at all.

Oof, it seems you are right.  Thank you for that important correction!

With respect, Sean, I believe that Fr Scott was a medicine student at one point in his life, but did not complete the training. Not that that disqualifies him at all.

For the record, Fr Scott did indeed complete his medical training, but as you say, Nadir, this contributes little to the argument.

Again, I am not weighing in on objections to vaccines, not valid moral objections to them but I will object to badly thought out medico-moral theology