From Wikw:
On 4 January 2021 UK newspaper The Telegraph reported that Oxford immunologist Sir John Bell believed there was "a big question mark" over the new South African variant's potential resistance to COVID-19 vaccines, raising fears that vaccines might not work as effectively on that variant strain. The same day, professor of vaccinology Shabir Madhi commented to CBS News that "it's not a given" that the new 501.V2 variant would be able to evade the vaccines, but that it should be considered that they "might not have the full efficacy"
We have to get a flu shot each year for different strains of influenza. Wouldn't it be funny if we had to get a new vaccine for each new strain of a coronavirus.
And the flu shot was developed for last years strain so most of the times is not effective for this years model.