Experts opinion series

Will we need further COVID-19 vaccine doses?


Obviously, we are learning as we practice. Unfortunately, because of the urgency of the epidemic. So one of the things I've learned in my life, is never make predictions, because there are many of them bound to be wrong. Okay, having said that, one point I would make is that there's a lot of talk about boosters. That is, individuals who have had two doses of the mRNA vaccines or other vaccines against COVID-19, the vaccine by Johnson & Johnson maybe being one exception, although even they are coming around to the importance of having more than one dose. But, anyway, so there's this basic immunization that is going on, where people are receiving, let's say, two doses of a vaccine and are having an antibody response. I mention antibody because that is really the principal correlate of protection against COVID. So, they have the antibody response, and the antibody response decreases, because the immune system has not developed sufficient B-cell memory. And that is normal. I mean, when we vaccinate children, we don't stop at one or two doses, because we know that their immune systems have to be primed and then recalled with another dose that is given approximately six months later, so that they have prolonged B-cell memory. So to me it was no surprise at all that after two doses the antibodies became lower and lower, reaching the point where susceptibility to infection became important. And although those illnesses have in general been modified, they have not been as serious as in people without antibodies, nevertheless there have been quite a few infections in people who received two doses. Well, obviously, the answer is to give a third dose four to six months after the first two doses, so that you recruit sufficient B-cells, so that the individual is likely to be much more immune for a much longer period of time. Now, of course, we don't have yet the concrete evidence for that, except in one way: if you look at the data concerning response to a third dose of whatever vaccine, you will see, in general, phenomenal increases in antibodies, which is entirely what I would expect because the individual has been sensitized by the first two doses, and the immune system has some recollection, but it’s not anymore producing high levels of antibodies. But you come along with that third dose, and the immune system wakes up again, and starts churning out antibodies. So, of course, we don't know yet how long that immune response will last, but my prediction would be that immune response after the third dose will last a lot longer than after the first two doses. So I believe that every individual should have a three dose regimen, and then we'll see just how long that immunity lasts.