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Yeah, well, I certainly haven't seen any explanation for why it would be intrinsically evil to use the cells of an aborted fetus for scientific research, much less to receive a medicine developed using such material.
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In the example of the guy drinking poison, it's clear that his object is ѕυιcιdє, because he is drinking to prevent himself from being taken alive. ѕυιcιdє is always sinful. The object isn't drinking in itself, because then he would be just as happy to drink a can of Coke in the same situation as he is to drink the poison. But if you grabbed the poison away from such a person and handed him a Coke (possibly quoting the old advertising slogan, "Have a Coke!"), he would get angry because you interfered with his real object. He is using death as a way of escaping the enemy, which is immoral. (Some people seem to think Coke is poisonous, so those people can replace "Coke" with "smart water" or whatever they like ).
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The object of taking medicine is to restore or protect one's health. That is a good object.

To quote your own words: "He is using death as a way of escaping the enemy, which is immoral."  Just as the recipient of an abortive vaccine is "using death as a way of escaping" COVID19, which is then likewise immoral.
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Well, the average person receiving the vaccine would not have this intention. If there is some inherent connection between receiving this vaccine and helping to abort children, I would certainly like to see it, but that's what's missing here.

Intention is irrelavent.  It is the object of an act which makes it intrinsically evil or not.

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Using cadavers for scientific research is as old as time, and I have never seen any claim that it is wrong to use a cadaver that was murdered, much less that it is wrong to receive treatments that depend on knowledge derived from the cadavers of murder victims. But this in no way takes away from the heinousness of the sin of murder.

Using cadavers who did not choose to become cadavers, as in the case at hand?

So you are saying the government would say, "Anyone who receives this vaccination, we will accept their participation as accepting the practice of abortion." I mean, who cares how they interpret your actions anyway? Someone getting injected with medicine is really not doing anything more than taking medicine.

Straw man.  Nobody argues that those who receive these vaccines are guilty of abortion.

Then what are they supposedly guilty of?

True, but the Tweet from +Strickland above comes close, saying that if Catholics are not going to refuse these types of vaccines, then abortion will never end.

It seems to me that he is suggesting (rightly) that such Catholics would be complicit in abortion (just as a man who buys stolen property is encouraging theft by creating a market for the stolen goods).

Also to be noted is the fact that COVID19 is fatal to almost nobody who was not already dying of something else already (i.e., It is fatal for well under 1% who contract it, on par with influenza mortality rates)

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There is no guarantee the vaccine will work (In fact, there is a growing awareness that the purpose of vaccination is to pollute human DNA/RNA, making them more prone to disease for the profit of the medical industry).

So when you throw those two observations into evaluating the morality of using abortive vaccines, the Vatican/SSPX argument seems even weaker (i.e., no necessity to use them).

True, but the Tweet from +Strickland above comes close, saying that if Catholics are not going to refuse these types of vaccines, then abortion will never end.

It seems to me that he is suggesting (rightly) that such Catholics would be complicit in abortion (just as a man who buys stolen property is encouraging theft by creating a market for the stolen goods).