A point Van-Tam made in the 'Downing Street briefing' this pm was interesting (enough to share on here), wrt the SA variant (B.1.351) - see
@roubaixtuesday 's link above for detail on reduced efficacy, small numbers in trial but likely 'an issue'.
He observed that the numbers of infections and geographic spread of Variant B.1.351 was still limited in UK and the vast majority of virus in the wild was the B.1.1.7 strain (aka UK/Kent discovered by genomics). (Worth pointing up the UK's superb genomics capability, quoted elsewhere as doing more than half the assays in the world, allows a better insight than anywhere to this. Is this effort government funded? (I don't know.)
Van-Tam also assessed that the B.1.351 did not seem to be more transmissible than the B.1.1.7 variant.
It was the substantially higher (1.5 (CI 1.3 to 1.7)) transmissibility of the the B.1.1.7 variant compared to the 'basic' (Jan-Sep 2020) which meant it 'out-competed' its predecessor and is now the dominant strain across the country. It also is one which resulted in the surge in cases and consequences from December onwards (along with other factors affecting 'R').
He deduced (on current evidence) that the B.1.351 variant would not out-compete the B.1.1.7 variant in UK so the effectiveness of the UK vaccination programme would be maintained.
Aiui