As many countries are going through another wave of infections, including some where the vast majority of the population has been vaccinated, many are starting to despair that we’ll ever see the end of the pandemic. In this post, I will argue that, on the contrary, not only is the pandemic already on its way out, but the virus will be relatively harmless after it has become endemic. This is going to happen not because the SARS-CoV-2 will become intrinsically less dangerous, although it might, but rather because what made the virus so dangerous was that nobody had immunity against it, so once it has become endemic it will infect fewer people and even those who end up infected will be much less at risk. Moreover, I will explain that, despite widespread anxiety about the emergence of new variants and the danger of immune evasion, the fact that SARS-CoV-2 is mutating will not prevent this outcome because of the way immunity works. Finally, I will argue that, although some people are calling to pursue the eradication of SARS-CoV-2 (as we have done with smallpox), we almost certainly couldn’t eradicate it even if we wanted to and that even if we could it wouldn’t be worth it.
SARS-CoV-2 is going to become mostly harmless
You may have heard that, as they evolve, viruses necessarily become less lethal because it makes no evolutionary sense for them to kill the hosts on which they depend for their survival and reproduction, but this is a myth and it’s not what I’m saying. The claim I’m making is based on a much sounder and more straightforward argument. But to understand why it’s true, you first have to understand that, as the virologist Dylan H. Morris explained in a great essay, what made SARS-CoV-2 so dangerous is not so much its intrinsic characteristics but the fact that it was novel, which means that nobody in the population had immunity against it.1 Indeed, while the debate about whether SARS-CoV-2 was “worse than the flu” or “just like the flu” dominated the early phase of the pandemic and to some extent is still ongoing, this question is not even well-posed because there is no such thing as the dangerousness of a virus simpliciter. The dangerousness of a virus is always relative to a particular context. This should be obvious if you consider the impact that the availability of effective treatments can have on how much damage a virus does. For instance, HIV was initially devastating because it invariably killed the people it had infected within a few years after symptoms onset, but thanks to the development of effective treatments infected people can now live a relatively normal life, at least in the developed world where people can afford such treatments. HIV has not become any less intrinsically dangerous, but it’s undoubtedly far less dangerous in societies where effective treatments are easily available.
In the case of SARS-CoV-2 though, the key contextual factor is what proportion of the population has immunity against it. Immediately after the emergence of the virus, the population was immunologically naive, which means that nobody had immunity against it beyond that conferred by the innate immune system against any pathogen.2 The amount of damage and disruption caused by a virus can differ wildly depending on whether the population in which it’s introduced is immunologically naive to it. This is because, when nobody in the population has immunity, 1) the virus spreads more easily and infects more people because everyone is susceptible to infection and 2) when people get infected they have a much higher chance of developing a severe form of the disease because their immune system does not yet have any weapons specifically tailored to fight this virus. So the same virus, with exactly the same intrinsic properties, can do vastly more damage in a population that is immunologically naive than in a population where everyone has immunity against it, either because they have previously been infected or because they have been vaccinated. That’s one of the reasons why entire indigenous communities in America were almost completely wiped out by pathogens brought by Europeans, even though people in Europe had been living with the same pathogens for centuries or even millennia and, while they were not by any means harmless to them, they didn’t threaten their existence.3
As more people get infected by SARS-CoV-2 or vaccinated against it, the virus will become endemic and continue to circulate following a seasonal pattern (because immunity whether acquired naturally or through vaccination is not 100% effective against infection and wanes over time), but the number of people who end up at the hospital or dead because of it will gradually decrease until we reach a sort of equilibrium.4 In some places, especially in developed countries where the vast majority of the population has already been vaccinated, this process is already well under way and you can see it on a simple chart: