I used the term "horse paste" because people in my country were literally going to "farm and feed" stores to purchase paste made to treat horses for parasites and then eating it, rather than taking the free and safe vaccine that had been tested for human safety and effectivness. Some of the horse paste eaters died of COVID, and many experienced side effects from the unapproved drug.

A lot of people are bad at evaluating risk. The internet makes it worse.

As to the "long term side-effects on the immune system of the Covid mRNA vaccine", I think it's safe to say that we would know them by now.

It's years later now, and most/all of the effects from the first round have long faded to a memory. Hence most folks have been boosted at least once. Millions upon millions of people have taken those vaccines, and some of us have taken them several times now. There hasn't been any uptick in all-cause mortality among those people that rose above the noise floor of the reports. In fact the vaccinated cohort tends to have died less often (as one would expect).

They're safe, they're effective, and they're cheap. They aren't perfect, but nothing is. Even if they do prove to be dangerous, the numbers show that the difference would have to be so minimal that your limited attention would be better spent installing new sticky things in the bathtub to prevent you from slipping and falling. Your death by those means are many tens of thousands of times more likely.