As UNSW Kirby Institute epidemiologists Raina MacIntyre, Valentina Costantino, and Mallory Trent have shown, the proportion of the population we need to vaccinate to achieve herd immunity varies substantially with vaccine efficacy. At 95 per cent efficacy, they calculate, 63 per cent of the population would need to be vaccinated to achieve herd immunity. If efficacy is 70 per cent, it rises to 86 per cent of the population. READ MORE