Chat about Novel Coronavirus - 2019-nCoV - COVID-19

I was pleasantly surprised to still have antibodies after so long as they keep saying on the news that they don't know how long protection lasts

I don't think I was clear enough, let me try and explain.

The fact you have antibodies now doesn't necessarily mean they've been lingering around since the original infection.

After an initial infection the immune system will keep antibodies around for a while in case it comes back soon but, over time (weeks/months but not years), the antibodies present in your blood will drop to undetectable levels. That doesn't mean your "immunity" is gone as the body remembers how to recreate those antibodies (and other associated immune system cells) if they are needed again the future.

The "they don't know how long protection lasts" refers to this latter point of how long the body remembers how to create the necessary cells to fight an recurrence of an infection. It doesn't just refer to how long the original set of antibodies remain in your system. They aren't the same thing.

It's much more likely that you have detectable antibodies in your system because you've been exposed to the virus again recently and so the body has created what it needs to create in order to fight the reinfection. In a couple of months the same test could return a negative result, and then a few weeks later (if you were exposed again) it may return a positive result, etc.

Immunity doesn't mean you never get reinfected. It's not some magic barrier that prevents the virus from getting into your body. It's how your body deals with the virus once it inevitably does get back into your body. It means your body is much better equipped to deal with reinfection before it gets to the levels where it starts to cause symptoms and/or (hopefully) before it gets to significant levels of the virus that could be transmissible to someone else.

Immunity also isn't binary, it's not simply "none" or "perfect". You could have had an original infection, then be jabbed twice, and still be one of the unlucky people whose well prepped immune system is still overwhelmed by the virus.