Ok, so I’m well aware that contracting SARS-CoV-2 only confers immunity for a limited duration of about a year or so, much like the other human coronaviruses.
But what I’m curious about is whether your immune system retains any memory of it or not? I mean, let’s say you caught COVID this time last year, and your immunity is starting to wane. What does that mean? Does it mean that it’s like you never caught it? Or is it more that you can contract it again, but might mount a more effective response/have less serious disease?
Where do you get this impression? I’m not aware of any study showing immunity dropping over time. Of course it might turn out that immunity starts to drop at a year, but I haven’t seen any data showing this (especially since we haven’t been able to study this thing for a year yet).
From the dozens of news articles that have said that they think it wanes over time just like immunity to other coronaviruses does, and that people can catch it twice they think. Most of the ones I’ve read have pointed to a 7-12 month duration of full immunity and waning immunity from there, but there’s not much data about what happens after that. Take a look at the previous post and that link pretty much mentions everything I did.
I guess you and I read different articles. I don’t remember ever coming across any data demonstrating fading immunity over time or reinfection on any meaningful scale.
Regarding your question, this article from Nature is hopefully useful:
With highly effective vaccines for COVID-19 approved, a critical question for informing health policy in a post-pandemic world is the maintenance of immunity against SARS-CoV-2. One year into the pandemic, a picture has emerged that immune responses generated against SARS-CoV-2 are, on average, in line with immunological predictions for this type of infection. Recent studies show that antibodies to SARS-CoV-2, including neutralizing ones, persist in the serum for at least 6–7 months following infection in 90% of subjects tested. Antibody kinetics are typical of those seen in many other infections. Levels peak 3 weeks post-symptoms with a subsequent contraction and plateau phase. Predicted from the presence of good quality antibodies, T cell responses are mounted as expected. T cells are crucial for orchestrating other components of the immune response, including B cell antibody maturation and production and the formation of long-lived memory cells.
What are the implications of these findings for a post-COVID-19 world? Will we achieve protective population-level (or ‘herd’) immunity? Will vaccinations eradicate SARS-CoV-2? Will repeat vaccinations be required to maintain immunity? We can look to our accumulated knowledge on the ecology of other human coronavirus (HCoV) infections to provide insights into these fundamental questions.
From articles I’ve read, re-infections have generally been mild cases. It’s probably safe to say that most people will have some protection longer than a year. Some of your confusion might be related to discussions about how long antibodies can be detected in the blood. But that’s only an aspect of immunity. It’s not the benchmark - it’s the thing we can most easily measure with current technology/knowledge.