In common with others, the virus that causes Covid-19 mutates as it spreads. Most mutations have little or no effect, but some can change the behaviour of the virus. Mutations in a variant found in the UK in September has helped the virus spread more easily and potentially more dangerously. Further changes in variants that emerged in South Africa and Brazil may help the virus resist antibodies induced by vaccines and Covid infections from the first wave.
Why would the vaccines be updated?
If scientists spot new variants of coronavirus that are resistant to current vaccines then the vaccines will need to be redesigned to make them effective again. The more people who have immunity, either through vaccination or past infection, the more evolutionary pressure there is on the virus to evolve around that immunity. And when there’s lot of virus around, as there is now, there are more opportunities for resistant variants to emerge.
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