Even a partially protective vaccine may reduce the risk of more severe illness. But that doesn’t mean we can let our guard down
- Julian Tang is a clinical virologist and honorary associate professor at the University of Leicester
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It’s hard to believe, but Covid-19 has been with us for more than a year, and like the rest of us, it is beginning to adapt. It isn’t unique in this regard – we know that viruses mutate all the time as they make mistakes during replication. Once a virus has entered a human host, it needs to find the right cell type in which it can replicate. During this process, it is exposed to human immune responses that exert pressure on it in various ways, causing mutations to develop. This often occurs in parts of the virus that are most exposed to the immune system, such as the outer protein. In the case of Covid-19, this is the spike protein that binds it to host cells, allowing the virus to enter and replicate.
The UK variant initially appeared last autumn in Kent with a mutation in the spike protein, along with a couple of amino acid deletions. This appeared to be more transmissible, but not any more clinically severe, and was later found not to impact significantly on the effectiveness of our then main Pfizer/BioNTech vaccine. Shortly after, we heard about the emergence of a new variant that contained a different pattern of mutations in the spike protein, which appeared to be spreading quickly throughout the South African population.
