In my previous posting on this website, I discussed what we all need to do to help keep COVID in its place. Masking, fist bumps, not shaking hands, vaccination, and so forth. We have to treat COVID like we treat colds, influenza and other highly communicable diseases because it spreads so easily through the air, from person to person, and even (to a lesser extent) by objects we touch every day like doorknobs, handrails, common pens, and so forth. There isn’t as much COVID around as there was during the pandemic of 2020-21, but it’s still out there, and we have to be careful. The same thing applies to influenza, RSV, cold viruses, and other obnoxious pathogens. They are around, and they can be dangerous.
But why are they still around? Didn’t vaccination eliminate them? No, it didn’t. Vaccination only caused these viruses (and I’m going to focus on COVID for this discussion, but the general principles apply to other viruses) to change to meet what to them is a threat to their existence. How does this happen?
Viruses are nothing but extremely small infectious agents which, when they get into a living animal such as us humans, cause the cells of the body to produce more virus, and those new particles infect more cells, and the cycle repeats itself over and over until the body either conquers the infection by producing an immune response, or dies. The total number of virus particles that may be produced during an infection is difficult to count, or even estimate, but it can be in the billions and even trillions. Or more. Especially if the infection is severe and the person is very sick. That’s right, even if all you get is a head cold, your nose could be producing a huge number of cold viruses. And every time you sneeze or cough, or even just talk or blow your nose, you are spreading a huge number of virus particles into the atmosphere where others can inhale them and catch the same disease. And those people may never know where the infection came from. For example, I had a bad head cold in January, and I still can’t figure out where I caught the virus. And COVID and flu and RSV and measles and a lot of other virus diseases are the same way. Bang, you’re infected. Your best bet is to get vaccinated so your immune system is primed to attack a virus much sooner than without the priming power of the vaccine.
But, you may or may not be thinking, how does a virus change over time to counter the attack by your immune system? What does a virus do to stay ahead of the vaccine? The answer can be simple, and yet at the same time, relatively complex. As I mentioned above, when you get infected, the virus produces zillions of particles. (Many of those particles are non-infectious, that is, they can’t produce disease. In fact, the ratio of infectious to non-infectious particles may be as low as one out of 100, or even lower.) But there are still zillions of infectious particles, and they are the ones we are concerned about here. When a person gets a vaccine, the response by the body is to attack the virus and destroy all those particles. Either eat them by phagocytosis, or inactivate them with antibody. But still, over the time the pandemic is going on, we still see variants of the virus appear and seemingly evade the immune response produced by the vaccine, and the vaccine has to be altered to attack the new virus. Where did the new virus come from?
Within those zillions of particles produced in each person, there are always a few particles produced which are slightly different. The process of producing new virus particles is never absolutely 100% effective. A few clunkers arise every now and then. The vast majority of those clunkers are non-infectious (this is in addition to the non-infectious particles I mentioned above.) But on a very rare (and I mean very rare) occasion, one or two of those clunkers will have just the right changes to make it evade the immune response of a vaccine, and go on to produce disease. And if that virus gets out and begins to spread, watch out—a whole new variant is spreading and a new vaccine is needed.
We tend to put this process in anthropomorphic terms, and say that the virus changed to meet the threat posed by the vaccine. The virus had nothing to do with causing the change, the whole process is strictly random. It just happened that one particle got changed by a random mistake when the particle was made, and it just happened to be exactly what the virus needed to make a new infection. The new infection usually turns out to be milder than the original because the virus “knows” that a milder infection, in which the patient stays alive longer, will produce more particles than a severe one, and that gives the virus a greater chance to produce more particles and more infections and thus continue to spread.
Of course, the virus doesn’t really “know” that. Viruses can’t think. The change is a consequence of the random change that gave the virus the ability to evade the immune response. Out of zillions and zillions of particles produced, and out of all the millions of people infected, only a very few particles are made that can evade the immune response. It’s a massively small number, really really tiny, so tiny it’s very hard to even comprehend. But that’s the way viruses work.