Can someone explain why this the mRNA vaccine (which tells your body to produce spike protein and thus mimic the virus) produces long-lasting immunity but the actual virus which is being mimicked does not do that?
There was a piece about this on NPR (I think earlier this week, but I can't find it right now).
It sounded like they're making some assumptions because the mRNA vaccine causes most people to produce a higher level of antibodies for a longer period of time vs the real virus. However, antibodies are not the only part of immune system, so it's possible that other parts of the immune system may still be effective.
The real answer is we don't know that yet conclusively, but we do know the vaccine is effective, so until we have a better understanding it's a good idea to be vaccinated regardless (especially if you have any risk factors).
I can't answer the mRNA half (because they're brand new and we just don't have that data yet), but I'm pretty sure I know where the "infection does not create long-lasting immunity" side came from:
Around 9-12 months ago, a study came out that said antibodies from infection last 3 months. They couldn't say any longer though because that study only had 3 months of data. Unfortunately, this was largely reported on as "up to 3 months", making a lot of people think immunity only lasted a maximum of 3 months.
Since then, now that we have more data, further studies have come up that keep extending that duration. Last I recall I think there was one that got to "at least 14 months"..? But these ones don't get as much spread as the original wrong reporting, so it got kinda stuck as "don't create long-lasting immunity".
It sounded like they're making some assumptions because the mRNA vaccine causes most people to produce a higher level of antibodies for a longer period of time vs the real virus. However, antibodies are not the only part of immune system, so it's possible that other parts of the immune system may still be effective.
The real answer is we don't know that yet conclusively, but we do know the vaccine is effective, so until we have a better understanding it's a good idea to be vaccinated regardless (especially if you have any risk factors).