Asked how many people need to be vaccinated for a vaccine to have any real effect, Public Health England’s head on immunisation Dr Mary Ramsey told BBC Breakfast: “Well, there is two ways that you could use the vaccine and the one we’re going for is to actually try and prevent people having serious disease and dying of this terrible infection.
“So we’re going to target people who are at highest risk, so we should very quickly see an impact in the numbers of deaths that are happening – it will depend a bit on what the background rate is at that time.
“But if we’re in a high incidence period, and we vaccinate the people at highest risk, we will begin to see an impact on deaths and hospitalisations quite quickly because we’re going to go for those people who are most likely to end up … in those situations.
“Later on, if it turns out that the vaccine interrupts transmission then we may give it to a wider group of people.
“And then we really need to get maybe half the population vaccinated to really see an impact on spread within communities.”