Good morning! It has been 326 days since the first documented human case of COVID-19. I have not heard a lot of major news about COVID-19 over the past day or so. We are in a rare period of calm in this pandemic; I urge you to enjoy it while it lasts. I also hope it lasts quite a while.
Question: what is the likelihood that taking an early, less-effective vaccine prevents a future, more-effective vaccine from working correctly? Or, to phrase is more positively: do you expect that different COVID-19 vaccines will work independently and provide stacking protection? (I find myself having unusually vaccine-hesitant thoughts about the in-progress COVID-19 vaccines, and I finally figured out that this is the question that's bothering me.) Thank you for writing this newsletter, reading it has become a welcome part of my morning routine!
This is a fantastic question. In the past, I've discussed the possibility that a bad vaccine could cause problems for the immunogenicity of a future, better vaccine. This kind of thing happens sometimes with influenza virus exposure; the first immune response in a person's lifetime to an influenza virus can be the strongest, and this strong immune response can actually get in the way of responses to later viruses--or vaccines. This concept is called "original antigenic sin," because virologists like to think we've very clever.
However, this doesn't apply to all viruses.
There is also the possibility that a bad vaccine could produce an "inappropriate" immune response that interferes with future immune responses. That's a little more complicated, but to give it in a nutshell, it's possible for a pathogen to induce an immune response that is not appropriate to that type of pathogen. For example, a bacterium might activate immune responses that are for larger parasites. When pathogens do this, it's often a response that evolves because it distracts the immune system from mounting a proper fight. Theoretically, a bad vaccine could also induce such an inappropriate response, and not be very effective. Later attempts to boost that response might still be blocked by this earlier inappropriate response.
I've not seen much evidence that COVID-19 has this kind of inappropriate immune response, though.
What I have seen so far is reasonable evidence that the vaccines being developed produce effective antibodies as well as T-cells. I've also seen reasonable evidence that antibodies have some kind of effect against SARS-CoV-2. Finally, and most importantly, I've seen clear evidence that a vaccine schedule involving a second "booster" dose improves the quality of antibody and T-cell response for the leading vaccines with available data.
This leaves me hopeful; if boosting helps these vaccines, then it's also possible that a mixed schedule of different vaccine types will boost the response. Our second-generation technologies for COVID-19 vaccination may simply work well as effective boosters for those of us who receive the first-generation option. This is a very optimistic view, and there is still much we don't know, but I do think that this is the direction that things may go.
A former colleague of mine, Dr. Florian Krammer, is an expert on vaccines and antibodies who has spoken on this topic in the past. He's very active on Twitter, and if you're on there, I'd recommend following him for potential future statements on this topic.
Question: what is the likelihood that taking an early, less-effective vaccine prevents a future, more-effective vaccine from working correctly? Or, to phrase is more positively: do you expect that different COVID-19 vaccines will work independently and provide stacking protection? (I find myself having unusually vaccine-hesitant thoughts about the in-progress COVID-19 vaccines, and I finally figured out that this is the question that's bothering me.) Thank you for writing this newsletter, reading it has become a welcome part of my morning routine!
This is a fantastic question. In the past, I've discussed the possibility that a bad vaccine could cause problems for the immunogenicity of a future, better vaccine. This kind of thing happens sometimes with influenza virus exposure; the first immune response in a person's lifetime to an influenza virus can be the strongest, and this strong immune response can actually get in the way of responses to later viruses--or vaccines. This concept is called "original antigenic sin," because virologists like to think we've very clever.
However, this doesn't apply to all viruses.
There is also the possibility that a bad vaccine could produce an "inappropriate" immune response that interferes with future immune responses. That's a little more complicated, but to give it in a nutshell, it's possible for a pathogen to induce an immune response that is not appropriate to that type of pathogen. For example, a bacterium might activate immune responses that are for larger parasites. When pathogens do this, it's often a response that evolves because it distracts the immune system from mounting a proper fight. Theoretically, a bad vaccine could also induce such an inappropriate response, and not be very effective. Later attempts to boost that response might still be blocked by this earlier inappropriate response.
I've not seen much evidence that COVID-19 has this kind of inappropriate immune response, though.
What I have seen so far is reasonable evidence that the vaccines being developed produce effective antibodies as well as T-cells. I've also seen reasonable evidence that antibodies have some kind of effect against SARS-CoV-2. Finally, and most importantly, I've seen clear evidence that a vaccine schedule involving a second "booster" dose improves the quality of antibody and T-cell response for the leading vaccines with available data.
This leaves me hopeful; if boosting helps these vaccines, then it's also possible that a mixed schedule of different vaccine types will boost the response. Our second-generation technologies for COVID-19 vaccination may simply work well as effective boosters for those of us who receive the first-generation option. This is a very optimistic view, and there is still much we don't know, but I do think that this is the direction that things may go.
A former colleague of mine, Dr. Florian Krammer, is an expert on vaccines and antibodies who has spoken on this topic in the past. He's very active on Twitter, and if you're on there, I'd recommend following him for potential future statements on this topic.