Yes, although “need” is not quite appropriate.
I presume you are referring to the various varrients appearing on our shores, from what I can gather the oxford vaccine works relatively well fighting the Kent varrient but less well with the South African. Oxford are already tweaking their vaccine, developing a top up to better fight the African varrient. I don’t know if the “top up” is a single dose, I think it is, but we will find out in due course.
The existing oxford vaccine is still very effective and if offered it you should take it.