How Vaccines Drive Covid Variants

Variants have been one of the hallmarks of this pandemic, with ever more infectious forms of the virus apparently mutating themselves into existence at regular intervals. However. it is easy to forget that prior to 2021 variants were a rarity and the only sign of our variant-ridden future was the emergence of the scarily named Kent variant (later renamed Alpha) late in 2020. The UKHSA Vaccine Surveillance Report started mentioning variants in May of 2021, but only in passing.  However, as 2021 wore on new variants started appearing more frequently, and in recent reports, there are 10 times more references to ‘variants’ compared to their debut. (To be fair, there used to be an entirely different vaccine report devoted to ‘variants of concern’, the Technical Briefings.)

But ‘variants’ weren’t simply a natural process of viral evolution – not when there were people to blame. By summer 2022 there had been multiple articles published explaining that it was the unvaccinated that created these variants, adding to the cries for (mandated) universal vaccination. I believe that the idea that it was the unvaccinated that were causing the problem arose due to a misunderstanding of the role of the mechanisms that drive viral evolution. While it is true that for many vaccines the main source of vaccine escape variants is the unvaccinated, this is only true for sterilising vaccines (which stop any viral load on infection), and isn’t the case for non-sterilising vaccines such as the COVID-19 ones. To explain this effect further we need to delve into the evolutionary process. 

Evolution is a natural process that explains how organisms become better at surviving within a given environment. It occurs when certain differences between otherwise similar organisms are favoured for some reason, resulting in that particular difference becoming more prevalent in the organism’s population. Evolution requires two things to occur – a population of the organism with heritable diversity and selective pressure.  The ‘population’ part refers to how many of the organisms in question exist; selective pressure refers to the ‘strength’ of the drive of the evolutionary process, which might be described as ‘survival of the fittest’, i.e., those specific organisms that happen to be better at surviving and reproducing will be more likely to pass on their genes to future generations, thus on average making the future species better at surviving and reproducing.

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