You're absolutely correct.

There is no sin that can't be forgiven, by having recourse to the Keys (going to Confession to a Catholic priest).

I think the belief that "the jab is an unforgivable sin" is the logical conclusion, once you accept that the jab is the LITERAL Mark of the Beast.

And unfortunately, many Trads, Catholics, and protestants believe that the Jab is the actual Mark of the Beast. Including such high-profile Trads as Sean Johnson. So I hesitate to call them idiots, though I am quite convinced they are wrong.

Many people, including myself, place little to NO hope of salvation for those who take the Mark in the end times. That could be unforgivable, or VIRTUALLY so.

But I hold that while the Jab might be a faint shadow of the Mark -- it is certainly not the Mark itself. Where is the Beast? Where is the Antichrist? It's supposed to be a single man; Scripture and Tradition tell us so. This very season, Advent, the Church has us listen to St. Paul addressing the Thessalonians who were having misunderstandings about the end of the world in the FIRST CENTURY.

2 Thess chapter 2:
http://drbo.org/cgi-bin/d?b=drb&bk=60&ch=2

[1] And we beseech you, brethren, by the coming of our Lord Jesus Christ, and of our gathering together unto him: [2] That you be not easily moved from your sense, nor be terrified, neither by spirit, nor by word, nor by epistle, as sent from us, as if the day of the Lord were at hand. [3] Let no man deceive you by any means, for unless there come a revolt first, and the man of sin be revealed, the son of perdition, [4] Who opposeth, and is lifted up above all that is called God, or that is worshipped, so that he sitteth in the temple of God, shewing himself as if he were God. [5] Remember you not, that when I was yet with you, I told you these things?
[6] And now you know what withholdeth, that he may be revealed in his time. [7] For the mystery of iniquity already worketh; only that he who now holdeth, do hold, until he be taken out of the way. [8] And then that wicked one shall be revealed whom the Lord Jesus shall kill with the spirit of his mouth; and shall destroy with the brightness of his coming, him, [9] Whose coming is according to the working of Satan, in all power, and signs, and lying wonders, [10] And in all seduction of iniquity to them that perish; because they receive not the love of the truth, that they might be saved. Therefore God shall send them the operation of error, to believe lying:
[11] That all may be judged who have not believed the truth, but have consented to iniquity.

CHALLONER NOTES:
[3] "A revolt": This revolt, or falling off, is generally understood, by the ancient fathers, of a revolt from the Roman empire, which was first to be destroyed, before the coming of Antichrist. It may, perhaps, be understood also of a revolt of many nations from the Catholic Church; which has, in part, happened already, by means of Mahomet, Luther, &c., and it may be supposed, will be more general in the days of the Antichrist.
[3] "The man of sin": Here must be meant some particular man, as is evident from the frequent repetition of the Greek article: 'the man of sin, 'the son of perdition, 'the adversary or opposer. It agrees to the wicked and great Antichrist, who will come before the end of the world.
[4] "In the temple": Either that of Jerusalem which some think he will rebuild; or in some Christian church, which he will pervert to his own worship: as Mahomet has done by the churches of the east.
[10] "God shall send": That is God shall suffer them to be deceived by lying wonders, and false miracles, in punishment of their not entertaining the love of truth.

I've heard this time and time again on catholic forums and so forth...

But I don't understand where people are getting this from?
Surely if the Vax is derived from aborted babies and you with full knowledge and consent of this, take it, it would be a sin , bow how can this be unforgivable

...Surely going to confession absolves sins?

And no, I haven't taken it, im just confused why people are talking about this specific sin bring unforgivable.

Can you cite posts where people on this forum have said it is an unforgivable sin?  I personally haven't seen any. 
[Except possibly to the extent that someone might say or imply that the jαb is the Mark of the Beast, as Matthew mentions in his post, and one assumes that taking the Mark is unforgivable.]

No one is any position right now to say this vaccine is damnig. I have yet to hear a priest at the pulpit even publicly damn people for it, Word for Word! IMHO, because some people are tithing due to working, due to being vaccinated! Now I have heard priests talk in elusive paraphrases the lead you to come to your own conclusions..I feel this is especially dangerous because then people feed off this gray area and start damning eachother. It's great!!

My point exactly..."uncategorcically" "could be"..."depending"..all words that are not absolute in nature. No black and white. To me that's skating around the question and giving diplomatic answers 

Some people here seem to be assuming that mortal sin is unforgivable. We are Catholics here and have the Sacrament of Confession.

Not questioning the institution or use of confession...question at hand is, is it labeled a mortal sin to begin with. Are priests saying openly in public if you get the vaccine your are in mortal sin. That's what I am asking.