We know that Covid vaccines reduce the risk of future infection by over 200%, and also reduce the severity of infection, compared to getting the disease. The official current thinking by the CDC is that vaccines are better than natural infection for Covid-19, based on that research and other considerations. (Added: See also this [thanks Yana!])
Surely, getting Covid would, for most people, cause a certain degree of immunity. That is what the immune system is for, after all. A vaccine imitates that process. It is entirely conceivable that getting a disease would be better than vaccinating in some cases. Remember the 2009 influenza epidemic? One study showed that getting that strain of influenza conferred better immunity than the vaccine available at the time.
The logic behind infection being better than a vaccine is usually this: The body responds, possibly, to multiple, and different, molecular configurations on the infectious agent, and learns to recognize them. A vaccine is almost always targeted to a smaller set of molecular configurations, so naturally a vaccine would not prime the immune system in as many different ways as the infection would.
That is a nice logical argument, but the empirical data clearly indicates it is wrong. The available vaccinations work better than infection in creating immunity. So why is this true?
I don’t think we fully understand this yet, but I’ll offer two lines of thinking. First, the somewhat more obscure but possibly very important. Remember, despite the fact that reporters and even doctors (and Facebook and Twitter self styled experts) only know about one part of the multi-part immune system, the b cell mediated anti-body response to an infection. There are other pars as well, including the t cell response, which amounts to t cell mediated death of infected cells, and the memory system for both t and b cell systems. Both of these systems work in concert with other aspects of the immune system, that involve for example cells that find a pathogen and bring it to specific sites in the body where it is interrogated, and responded to.
There is research to suggest that for some diseases (not Covid specifically but other respiratory viruses) an infection may elicit a very rapid response by the t cell system, which does the infection in fast enough that the b cell system does not fully develop an “evolved” memory response to use later in the event of a second infection. However, over time, with repeated infections, all of the various parts of the adaptive immune system figure it out and fully respond, and now the individual has excellent immunity.
Personally I suspect that this explains the curious phenomenon that no children or young adults are zero percent likely to get a cold, but lots of people in their 70s or older claim that they never had a cold in their lives. They did, they forgot, and in the mean time, their immune system developed a strong response to common colds. This is an untested hypothesis, so don’t go around thinking it just yet.
The larger point is this. If that research is meaningful, it may be the case that the immune system is capable of tripping over itself, so a natural infection produces a less than idea result. Meanwhile, a vaccine is designed to not do that. Remember, if we have a few vaccines for a given infection, those vaccines represent a small subset of many potential vaccines that were tried out and either gave indications of ineffectiveness or bad side effects. Perhaps those earlier variants of the vaccine are analogous to less than effective immune responses to natural infection.
Which is a nice segue into the second idea. Imagine a target in a shooting range, one of those outlines of the body with a few areas designated (by bull’s eye symbols) as places to shoot. Imagine firing a gun semi-randomly at the target and maybe hitting it in a few places. If you do that a bunch of times, you may now and then accidentally hit the head, and have a clean kill. All the other shots are either totally ineffective, or only “wound” the target. That is natural immunity to a natural infection.
Alternatively, you shoot the target in the head once and it is dead. One bullet, one shot, but a perfect shot aimed at exactly where you have to shoot to have the best result. That is a carefully designed vaccine. It doesn’t matter how many other body parts (surface configurations of molecules on a virus) the natural immunity responds to, if there is one main configuration (in this case, part of the spike protein) that the vaccine focuses on. And no, the virus doesn’t easily mutate in such a way that the spike protein is different enough that it can’t be targeted. This is a part of the virus that is highly conserved. It cant change much, or the individual virus with the change can’t reproduce. A target can’t exist without a head. It will always have a head, and if you can always hit the head, then you always win, and all the other strategies are lesser.