They didn't know. And to begin with, we know they didn't want to do anything, so by the time they did do so they were forced to do more. And "more" means much more because that's the nature of exponential growth: they thought the doubling time was about 7 days and it was more like 3 days, and the main measure they had was hospital admissions which was (and is) a lagging measure.
In what context did he say that? As I understand it there was significant uncertainty in early 2020 that vaccines could be available quickly enough or would work effectively enough to be useful; among the Oxford group (and the mRNA people) there was more confidence (the Oxford group had SARS and MERS vaccines and the mRNA people had experimental flu vaccines that had tested well) but I don't think anyone had confidence in manufacturing.
In retrospect I think the NZ government can be happy about their choice since it did allow the population to be vaccinated before exposure but even in that case I think the initial decision was mostly about delaying in the hope that something would happen rather than specifically about a vaccine (though a vaccine was always one of the hopes).
I had more trust in the protect the elderly/vulnerable (those in their 80's and 90's not so much the under 65's) strategy which is what the Great Barrington Declaration was about. Some say, ah but people of all ages can die of it, but to put things into context a little bit, humans get sick all the time, it's part of being human and as Chris Whitty explained many people will never even catch the virus, won't even get any symptoms. The average age of death is 82. Life is a risk. We can't expect to eliminate all risks (at any cost), especially when it means others suffer as a result, like those requiring urgent treatments for other diseases and illnesses.
I think it would be a fair statement to say if we put $11 trillion and such world wide effort and determination into diabetes research, cures and testing more good would of come of it. Do you know how many people are living with undiagnosed and untreated diabetes across the world? how many die of food poisoning every year? and yet, it is claimed that it was about saving lives, yet beer and fags are still readily available in the shops. Very little has been done about people driving whilst using their mobile phones. There are all sorts of ways lives can be saved without destroying everything and leaving us huge debts.
Chris Whitty At Government Daily Briefing 11/05/2020.
“A significant proportion of people will not get this virus at all, at any point of the epidemic which is going to go on for a long time.
Of those who do, some of them will get the virus without even knowing it, they will have the virus without even knowing it, they will have the virus with no symptoms at all- asymptomatic carriage, and we know that happens.
Of those that get symptoms, the great majority, probably 80%, will have a mild or moderate disease,-might be bad enough for them to have to go to bed for a few days, not bad enough for them to have go to the doctor.
An unfortunate minority will have to go as far as hospital, but the majority of those will just need oxygen, and will then will leave hospital, and then a minority of those will end up have to go to severe and critical care, and some of those sadly will die, but that’s a minority, it’s 1% or possibly even less than 1% overall, and even in the higher risk group..Uh..this will be significantly less than 20% i.e. the great majority, even the very highest groups, if they catch the virus will not die”