I have a vax scar that looks exactly like this. It's not the MMR as this tweet claims; I had that one too and there is no scar. This was a smallpox vax, which do commonly leave a mark, and I got it when I was five. I don't remember, but I've been told I was sick for a week.
Clearly, I recovered. Maybe that colors my view on this issue, I dunno.
But to truly understand the position of the individual that tweeted this, go look up some pics of actual smallpox cases, and then visit Wikipedia to learn about how many die right off the bat (some with horrible variations like hemorrhagic smallpox) and how many others survive, many with only massive scarring, but others with lasting internal damage and little-understood post-viral syndromes.
I like a further way to put it into perspective and to show how far as global society we haven fallen since:
The WHO launched its vaccination campaign against smallpox in 1958 and it lastet until 1977. So during the height of the cold war the West, the Sovjets, China and all of the Third world came together, to get everyone vaccinated. While pointing nuclear weapons at each other they all still understood what a shitty disease that is and worked together on this issue, because they all saw it as a responsibilty to rid the world of that disease.
And they fucking did it. They vaccinated almost everyone in the world so the disease is considered extinct. Today we get Karen instead who'd rather have half the elderly in her community die, than wear a mask while shopping.
Well, right now I regret wearing a mask during covid because the elders are getting us all the shit right now with authoritarian liberalism and anti-climate protests.
My mother also got the smallpox vaccine and had a permanent scar from it. I pointed it out as a small child and she told me about it, I asked my dad and he had one too. I thought it was cool, like a rite of passage where one day I'd be old enough to get my own permanent vaccine scar. But then they had to go and eradicate smallpox, saving countless lives. Bummer, dude.
A bunch of these people are scared of needles and are looking for any excuse not to get a needle. They don't want to feel alone so they spread lies so others don't get it either.
Some are really that irrevocably convinced that vaccines are the harmful thing. They don't know how to question things properly and they end up following whatever lead they got hooked to. It's a failure of modern education and society to fail to question things correctly. Questioning without logic or reason or being willing to accept you are wrong is unproductive at finding truth. However it's a potent way towards confirmation bias.
They also might just not understand the answer. Like the "risk" they claim is a possibility, the side-effects are real. But the part they never seem to bring up is that the possibility of those severe side-effects is generally less than 1 in 10 000. Instead they talk about it like it's a near-guaranteed outcome.
I think its mostly snake oil sellers and their radicalized victims. The flatmate of my girlfriend was an anti vaccers. She bought some extract from local plants for a 100 € because the guy told her it would soak up the vaccine from the body when there will be mandatory vaccinations.
Of course there were no mandatory vaccinations, having some hobo made tincture working against an mRNA vaccine is clearly ridicilous and she could have collected these plants in the next park and made the extract with some high proof alcohol for less than 5€.
One of the leaders of the covid conspiracy movement in Germany fled to Tansanie having defrauded his followers of more than 10.000.000 €
If you look into conspiracy products it is insane. Some wooden pole with some Glass balls in it? Yeah thats some energy protector, only 6.000 €
And if we trace the source of these conspiracy theory lunatics/scammers, it all comes back to social media. Arguably, that's a worse disease than smallpox or covid.
I think almost everyone from S. Korea and other parts of Asia have that small pox vaccine scar on that top part of their arm. American soldiers that deployed overseas all have that small pox vaccine scar as well. Taking vaccines and medication is basically mandatory for military.