It’s a real scientific term since the 1960s.  Basically, when you’ve already been immunized for a virus and then you get immunized for a variant of that virus, your immune system tends to just produce the original strain’s antibodies from memory all over again and only very little for the new variant.  It’s kind of like putting a nail in the wall to hang a picture on.  Get it right the first time or don’t try at all.  Even it you eventually hit the solid wooden stud on the second or third, or fourth try you’ve got all those ugly holes left behind.  There could be a lot of ugly holes around when they decide to update the boosters from the original spike protein in the current experimental “vaccines” to something closer to its current form going around now.

It’s short but awfully technical.  And it won’t be on the exam…

https://www.cambridge.org/core/journals/infection-control-and-hospital-epidemiology/article/original-antigenic-sin-a-potential-threat-beyond-the-development-of-booster-vaccination-against-novel-sarscov2-variants/C8F4B9BE9E77EB566C71E98553579506#

“A phenomenon called “original antigenic sin” (OAS) was firstly proposed by Francis in 1960. This phenomenon occurs in the second exposure of the immune system to a similar pathogen to which it has previously been exposed. In this situation, the immune system progresses to the memory response, generating cross-reactive antibodies that may not be effective against the new pathogen. In addition, it has been speculated that overproduction of memory B cells could compromise the activation of naïve B cells capable of producing efficient and novel antibodies.  In this way, OAS can trigger immune evasion of the emerging variants in those who had been affected by or vaccinated against former versions of the pathogen.”

It would have been better if they had never been born at all!  Sorry, if they had never been vaccinated at all.