There's so much noise on both sides that the actual immunology gets completely lost. I want a clear, mechanism-level explanation of what happens in your body in the 2 weeks after a shot, step by step.
serious question: if the mechanism is so well understood, why does immunity from some vaccines fade so fast while others last decades? genuine gap in my understanding, not a gotcha
actually a good question. short version: it depends on whether the vaccine generates long-lived plasma cells in the bone marrow. some do, some don't, and we don't fully understand why. influenza wanes fast partly because the virus mutates but also because the immune response itself is short-lived. tetanus lasts decades because of how the memory B cells are maintained. the mechanism story is well understood in parts and genuinely murky in others.
Really glad someone framed it this way. The mechanism story is genuinely interesting and almost never gets told clearly. Antigen presentation, T-cell priming, the germinal center reaction, affinity maturation. It's a multi-week biological process that most explainers skip entirely in favour of "your immune system learns to fight the virus." That's not wrong, just not useful.
One thing that rarely comes up in these conversations: the adjuvant matters enormously. Aluminium salts, AS04, MF59. Different adjuvants trigger different innate immune responses which shapes the downstream adaptive response. The vaccine isn't just the antigen. That's part of why you can't just take the mRNA sequence alone and assume you know how effective the vaccine will be.