**11. Vaccines and their efficacy**

A lot of viral evolution just comes down to statistics and a particular mutation that may confer the ability of the virus to make more copies of itself or to be stickier to cells. After that over time, it becomes more predominant in the population, because of that selective advantage it has and this is exactly what has happened with variants being detected around the globe [71, 79]. The variants reported are usually designated by their regions or locations where they were first found (B.1.17, B.1.351, P.1, and B.1.427/B.1.429). For example, some detected in California, South Africa, etc. [38, 80] (summarized in **Table 2**). But some variants were simultaneously found in



#### *Perspective Chapter: Tracking Trails of SARS CoV-2 – Variants to Therapy DOI: http://dx.doi.org/10.5772/intechopen.106472*

#### **Table 2.**

*Advanced SARS-CoV-2 vaccine candidates.*

many locations at the same time like a variant was first detected in the UK, South Africa, and Brazil which were already circulating in the US. This dilemma is still unanswered and may dampen the effectiveness of available vaccines [46, 66, 81]. When researchers talk about vaccine efficacy, a lot of attention is paid to antibodies, specifically neutralizing antibodies. The leading COVID-19 vaccines all induce neutralizing antibodies, which bind to the virus at a few different sites on spike proteins called epitopes [43, 81]. These neutralizing antibodies thus block the virus attachment to cells but to contrary, the evolving mutations in the virus are most worrisome in terms of vaccines, as they affect neutralizing antibody binding sites on spikes [81]. So, the first step in understanding how a variant will impact vaccine effectiveness is to analyze where the mutations are. But while this provides important clues, it does not give the full picture. **Table 2** below summarizes the available vaccines till now and their efficacy.
