"For a vaccine with 100% efficacy that gives life-long protection, the level of herd immunity as a proportion of the population, pc, required to block transmission is [1 – 1 / R0], where R0 is the basic reproduction number.16 Given an R0 value before lockdowns in most countries of between 2·5 to 3·5, we estimate the herd immunity required is about 60–72%. If the proportional vaccine efficacy, ε, is considered, the simple expression for pc becomes [1 – 1 / R0] / ε. If we assume ε is 0·8 (80%), then the herd immunity required becomes 75–90% for the defined range of R0 values."
Still, it's better than nothing even without achieving herd immunity.
"For a vaccine with 100% efficacy that gives life-long protection, the level of herd immunity as a proportion of the population, pc, required to block transmission is [1 – 1 / R0], where R0 is the basic reproduction number.16 Given an R0 value before lockdowns in most countries of between 2·5 to 3·5, we estimate the herd immunity required is about 60–72%. If the proportional vaccine efficacy, ε, is considered, the simple expression for pc becomes [1 – 1 / R0] / ε. If we assume ε is 0·8 (80%), then the herd immunity required becomes 75–90% for the defined range of R0 values."
Still, it's better than nothing even without achieving herd immunity.