I do not believe that the evolution of SARS-CoV-2 is what’s driving the virus’s continued spread. The coronavirus remains good at propagating itself because most of us still are susceptible to it; we are not immune, and it can still find new hosts to infect relatively easily.
In the same issue of Cell that published the Korber paper, the viral epidemiologist Nathan Grubaugh and colleagues argued that the “increase in the frequency of G614 could be explained by chance and the epidemiology of the pandemic.”
In other words: The next time you compare different outbreaks and start wondering or worrying about the variations, assume first that those variations have to do with conditions on the ground, rather than anything about the virus itself, like a new mutation.
Consider, for example, the wave of SARS-CoV-2 infections that has hit Australia since June. While there has been a major outbreak in the state of Victoria (peaking at around 700 cases per day), the one in the state of New South Wales has been minor so far (with a daily case count usually around 10) — yet both have been caused by the same variant of the coronavirus, the one with the D614G mutation.
The precise reasons for these differences are still being investigated, but one may be, simply, that because the outbreak hit Victoria first, the health authorities of New South Wales had more time to prepare.
Mortality rates, too, differ between locations, and in some places the virus may appear to kill more people. But again, these variations probably say less about the virus than about differences in how the disease is being treated, or where the virus has spread mostly among vulnerable populations, like people in nursing homes.
What’s more, even if the D614G mutation does increase the virus’s infectivity in humans, that fact probably doesn’t have any major implications for our prospects of developing an effective vaccine. The mutation does affect the spike protein, but not the part of it that the neutralizing antibodies of the human immune system target when the body defends itself against infection.