How vaccination affects the evolution of viruses

How vaccination affects the evolution of viruses

The SARS-COV-2 vaccination campaign is one of those that has reached unprecedented proportions in the world, and researchers ask how these biotechnologys change the evolution of pathogenic agents.

Researchers in mathematics and biology, far from creating a fear of disinformation against vaccinations that vaccines can produce a more dangerous and deadly virus, ask how vaccination, biotechnology, which has become an integral part of our lives, will affect the evolution of pathogens, and they propose conceptual categories to determine and study the adaptation of the virus to the environment, with particular attention to the case of the Covid-19 pandemic.

Understanding pathogen evolution

First of all, researchers suggest a rather classic definition of how to treat pathogen adaptation to the environment: either by looking at absolute growth rates, i.e. the average number of people who have infected the option, or by considering relative growth rates, i.e. by comparing absolute growth rates with absolute growth rates of the original option.

Now we know that to spread the option, the speed of its growth

Four types of options

In order to adapt, the options use several mechanisms: immune evasion.

All these considerations led the authors to the concept of two main families of pathogenic options: "universals" and "specialists." If we imagine an option that has been adapted using some of the immune mechanisms mentioned above and has adapted to the naive population, we can say that this option is universal, that it will spread better than the original strain, regardless of the type of population in question. On the other hand, if the option is adapted only to the already immuneised populations, it can be said to be a specialist, that is, it will spread better than the original strain in the already immuneised populations.

In these two families, one might also ask whether immunity would suppress or facilitate infection, and in order to take account of that particular circumstance, the authors created two additional categories: the options that were suppressed by immunity and the options that promoted immunity; while the growth rate of the former would decrease from each infectious or vaccine campaign, the growth rate of the latter would probably increase.

How does vaccination affect the evolution of viruses?

Before discussing the authors ' hypotheses about the various versions of SARS-COV-2, it is important to recall that most vaccines interfere with the evolution and adaptation of pathogens for two main reasons: as a preventive intervention, the vaccine limits the replicability of the virus in the host body, thereby limiting the number of generations and hence the transmission of the virus; in addition, vaccines usually cause a broad immune response to the virus, and many genetic changes are usually required to adapt to the immunity offered by the vaccine.

In the case of SARS-CoV-2, researchers suggest that Alpha and Delta options are classified as "universal" with reduced immunity; indeed, according to epidemiological data, Alpha and Delta have spread in countries with low vaccination rates to the same extent as in countries with high vaccination rates; this makes them universal, since they are distributed regardless of whether the population is naive or immune; on the other hand, while the data are less convincing, it seems that the rate of growth of these options has decreased as the rate of vaccination has increased, which has resulted in the classification of depressed universals.

On the other hand, Omitron is undoubtedly a specialized option suitable for immune populations, given its late start, when the immunity acquired by natural infection and vaccination coverage were widespread. Preliminary observations suggest that it will also be repressed by immunity. It appears that no immune-mediated options have emerged from the original SARS-CoV-2 strain.