I would think so - if a vaccine was 70% effective then if you vaccinate 100 people you'd expect 30% could become infected despite being vaccinated which is the same result as vaccinating 70 people with a 100% effective vaccine.

This is particularly concerning with the new 202012/01 strain being relatively 1.74 times more transmissible. If the original Corona virus had a natural R0 = 3 , 1 - 1/R0 = 0.66 i.e. 66% requirement of population to be vaccinated to achieve herd immunity, then with the new variant R0 = 5.22 the same calculation works out to 80% of population and won't be achieved with a 70% effective vaccine.