In this educational video Dr. A addresses the common question of whether immunity persists after a COVID‑19 infection. He explains the basic immunology of antigen presentation leading to two arms of adaptive immunity: T‑cell responses (cytotoxic and memory T cells) and B‑cell responses (antibodies and memory B cells). He highlights recent research—summarized in a Nature review of four papers and a Cell study—that shows both antibody levels and T‑cell activity remain detectable for up to a year after infection, even in people who were asymptomatic or had mild disease. Importantly, memory T cells can reactivate memory B cells to produce new antibodies upon re‑exposure. The data suggest that most individuals develop robust, long‑lasting immune memory, making reinfection and onward transmission unlikely, except in cases of immunosuppression or when a substantially mutated viral variant emerges. Dr. A advises viewers to consult their personal physicians regarding vaccination and to recognize the limits of current knowledge, noting that commercial T‑cell testing is becoming available but still less common than antibody testing.
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Hey, it's Dr. A. Just wanted to answer probably one of the most common questions that I've got in the last number of months, and that has to do with the idea of immunity to COVID once you've had COVID, and there's been a lot of back and forth. If we consider that we're really very new into this new version of the coronavirus that we're dealing with as humans, the SARS-CoV-2, And so we just don't have a lot of history. So early on, we were hearing a lot of reports of things like people having recurrent infections, so they would get it and then they'd get it again. Turned out that's happened, but it's quite rare and only happens under very certain circumstances, as far as we know right now. And then there was a lot of data that came out that was a little confusing early on, saying, well, it doesn't look like people are keeping their immune proteins, their immunoglobulin response, the B cell response, which is concerning because that's some— something that we like to keep as a memory part of our immune system. So because so many people at this point have had COVID as a natural or native infection, I get a lot of people asking, well, you know, will I lose my immunity? What's, you know, is there any research on this, etc.? So thankfully, people are obviously keeping track of a lot of things around coronavirus, COVID, SARS-CoV-2. We'll just call it COVID for today, and the thing that we want to keep in mind is that what we're seeing in the research that is more modern with respect to the last, say, year and a half— it's sort of funny to say modern, but within the scope of COVID— is that indeed your immune system is responding like it is supposed to if you do have an infection with COVID COVID, and there is maybe some differences a little bit between asymptomatic and early infections with low symptoms to, you know, people with more robust symptoms that they have going on, but the bottom line is that you're having an appropriate response. So just, I'm going to do a separate video that I'll link below about this, but just a little Cliff Note version of What should you have as memory for your immune response? Well, generally speaking, after you have the insult of the infection into your life, you have the presenting of an antigen. So infection in this case is the antigen, and your immune system presents it to the specific immune functions in your body. And there's 2 major sides. It gets real complicated, but just keep it to 2 major sides. and that is the T cell, which makes cytotoxic or killer T cells and memory T cells, and then there's the B cell function, which is separate, and that makes your antibodies, your immunoglobulins you've heard about, so like IgG or IgM, IgA, those sorts of immunoglobulins. So you get down to the immune system-specific function, and the T and the B cells do their own thing after antigen presentation. Now in real life, the T cells often are triggered first from antigen presentation, and very quickly the B cells are triggered, so then they go into their own production. So if it's T cell, it's going to make killer T cells and memory T cells. If it's a B cell, it's going to make antibodies, the immune proteins that we've talked about in other places. Now because they're triggered almost at the same time, The nice thing about the way this is turning out with COVID is T cells can reactivate B cells later on, and they can also activate them in the beginning. Why is that important? Because earlier data showed that while some people had extinguishing of B cell antibodies, so they didn't make antibodies very long, that they kept their T cell responses, so their cytotoxic and memory T cells. And there's other T cells too, but we'll stick to those guys. The important thing about this is the T cell can actually turn on a memory B cell and make it make antibodies again. Now, what the latest or more recent data is showing, and I will put links to these in the description box, is a couple of things. So one of the things is with respect to the B cell side, the antibodies, Nature News, so Nature is a large set of journals, they have Nature Medicine and all sorts of other things, very respected journal, did a review of 4 papers around B cell activity and COVID, a nice update, and again I'll give you the reference to that, but basically what they said is that after COVID infections, your antibodies persist, as opposed to earlier reports that said they went away. So your antibodies persist. What really happens is they drop after the acute infection, so in the first 4 or 5 months they go down, but out 11 or 12 months later they're still present. And earlier data that was, you know, early in the infection, so we didn't have a lot of time to look at people, was saying, oh, they go down, so maybe they're going to zero, and they got people all worked up. Well, it turns out you keep most of your B-cell antibody activity. And the most important part that the data showed that they review there is that the B memory cells, so the B memory cells which can be turned back on to make new antibodies, are still there, so they don't go away. So the antibody side, the B cell side of your immune system, is intact. It works like it's supposed to, and this is whether you have, you know, no symptoms, minor symptoms, or real bad symptoms. With COVID On the T cell side, so the killer cells and the killer T cells and the memory T cells, what a report in a journal called Cell, which is a very, again, very respected journal around cell function, cell biology, all those sorts of cool things, is that when they look at specific COVID T cell activity, you make not only the cytotoxic, the killer T cells, while you have the infection, but you also build up memory T cells, and just like the B cell memory cells that are so important, T cell memory cells are equally important. So if you get exposed again, they can sort of reanimate and make new killer T cells and new antibodies, and so that's sort of a win-win situation. That's what we're hoping would happen. In people with very mild or asymptomatic infections or low-grade infections— so in high-grade infections, the T cells are known to be produced and stay for a long time and all that stuff, but we weren't sure about mild or asymptomatic cases. Well, it turns out even in people with no symptoms, if they were exposed, they will build up and make T cell responses. and they will have memory T cells that will persist for the long term. The other thing that they said was because there are a subset of people where the B cells, the antibody-producing cells, don't maintain at very high levels, they check these people out, and people with little or no B cell antibody production to COVID after they had COVID still make the T cells, the killer T cells, and the memory T cells. The important part about that is a memory T cell can go tell a memory B cell to reanimate and make antibodies again for you. So if you are of average immunity, and by that I mean almost everybody, there are some people who are immune suppressed, there are some people who are on drugs that suppress their immune system, so that may be a different story, but if you're anybody in the bulk of humanity and you have been exposed even without symptoms, The chances of you having both a robust memory T cell and B cell response in your body is actually quite large, and even if you can't measure antibodies, say the IgG is the most common antibody they measure for COVID, you can't measure any in there, what the latest data says is you still have memory T cells, and if someone exposed you to COVID again, The memory T cells, if that's all that's left, will reanimate literally and go and make killer T cells and activate the B cells again as well. And as I said, the earlier— the other data showed by Nature when they did their review of the 4 papers shows that we persist and continue even with low levels of circulating antibodies. We persist with memory B cells to make more antibodies. So really it's It's very good news. It's very comforting, at least if you look at it from, you know, a physician immunologic point of view, to know that your patients who have had COVID infection have very good, robust native immunity. If they're on immune suppressive drugs or they have other, you know, immune suppressive disorders, you have to look at that, want to do some testing, we're now finally getting some really good, or at least serviceable, commercial T cell testing. We can always test antibodies. T cells are a little bit harder, but we're getting into those. So, as I say, in the average person, we have a very high index of comfort that you're going to have a good B and T cell activity, and that's going to persist. And so this answers a lot of the questions that I get, which is, Well, I already had it, and whether it was a small, medium, or large problem for the disease, you know, people ask questions like, could I get it again? It's possible, but it's very, very unlikely, and if you have these T and B cell memory cells in there and you've got antibodies floating around, it's sort of like any other disease that you have immunity to now because you've got the disease. You are Both unlikely to get it again, you're also unlikely to spread it to anybody. And so a real, you know, good, you know, thing as far as comfort level with regard to, you know, native immunity, natural immunity, which means you've just got the infection and now you have the immunity, is that you are very, very, very unlikely to ever get it again or even spread it to somebody. Now the papers, all the papers end this way, which you have to because we can't predict the future. Remember, science can look at what we see right now based on what we know right now. It can, you know, forecast and guess, but it can't predict the future. So the one caveat that they always put in the end of the paper, so I'm going to put it in the end of my discussion here, is if you have a mutation of a virus such as the most common thing is you can have the common cold this year and get it next year too because it's a different virus when it comes around. You can get this with influenza or whatever, so if you get an actual big mutation of the virus, then, you know, all bets are off as far as the immunity you have right now, but as far as SARS-CoV-2 goes, if you have survived an infection, even an asymptomatic one, the data shows that you have very robust immune memory, and as I said, unless you're on immune suppressive drugs, or some other problem, your chances of getting the infection again or spreading an infection to somebody else are almost zero. So I think that that's very, very useful information, very good information to have. Now, the other follow-up question I always get with this, which I'm going to say what I always say, which is never get all your medical information from YouTube. That's a very bad way to get your medical information. This applies there. Everybody is individual when it comes to, okay, I've had COVID and, you know, one doctor told me I should still get the COVID vaccine, the other doctor said I shouldn't, what do I do there? Well, you need to resolve that with maybe a third practitioner or, you know, get everyone's heads together. There might be some reason with your immune system particularly why someone's recommending that, and that's between you and your doctor. But based on what I see here and based on what I see in the data, again, your chances of both getting it and also transmitting it are almost zero, really, with an intact immune system. So that's the goal of today's talk, is really talking about the T and B cell activity after a COVID infection, even if you had low or no symptoms. And what we know now is that we do still retain both sides of our immune function, and so if we get exposed again, it will activate quickly, and just like if you had chickenpox when you were a little kid, if you're old enough like me to have done that, you never got chickenpox again, right? Well, unless you got immune suppressed or something else happened. It's the same thing with this virus at this point. All right, I'm Dr. A down in the comment box, which is a little dropdown menu, and usually on the lower right corner on the YouTube thing there's a little chevron or a little arrow. Click on that, you go to the description. I will put the links to these 2 papers in there, and you can take a look yourself and see what you think. Thank you very much, and I'll see you all again.
