pfizer vaccine effective against british variant B oth the Pfizer … Both the Pfizer/BioNTech and the Moderna COVID-19 vaccines may be less effective against the B1351 variant first identified in South Africa, although the latter vaccine could offer good protection against the B117 variant first seen in the United Kingdom, according to two letters published yesterday in the New England Journal of Medicine.. The study also noted that both vaccines work against the UK variant of the SARS-CoV2 virus (VOC 202012/01). They were much less effective against the B.1.351 variant. The two coronavirus ...