デルタ株への感染を防げる確率(ファイザーで70%越)は変異前のSARS-CoV-2への感染を防げる確率(mRNAワクチンで90%前後)よりは低いけれど、ワクチンを接種しない理由にはならないんじゃないかと思うんだ。
> For the Delta variant, recent studies from England and Scotland have noted reduced effectiveness of the Pfizer-BioNTech vaccine against confirmed infection (79%) and symptomatic infection (88%), compared with Alpha (92% and 93%, respectively). During two recent rounds of a national population survey in England when Delta was the dominant stain, 2-dose vaccine effectiveness against PCR-confirmed infection was 72% and 73%, respectively. A study from Canada demonstrated 87% effectiveness against symptomatic illness ≥7 days after receipt of the Pfizer-BioNTech vaccine.
https://www.cdc.gov/coronavirus/2019-ncov/science/science-briefs/fully-vaccinated-people.html