Deutsche Welle and herd immunity

A couple of weeks ago I was interviewed by a journalist from Deutsche Welle – a German broadcaster and news agency with an international reach. The result is an article linked here.

The key points: Maths for herd immunity is deceptively simple, but there is a lot of complexity that it tries to capture.

Politicians often need a goal that can be reached and the 1-1/R_0 formula can provide this, but the uncertainties associated with what R_0 value should be used and how vaccination affects the immunity render the actual value basically useless.

This would not have been a problem, was it not for the natural optimism of politicians and societies, often to the point of reckless disregard of the warnings by epidemiologists, modellers and public health scientists. Just to stress this:

There is no “magic” vaccination level that once reached it will make us all free – see the newest outbreaks in Israel.

We need to keep vaccinating, to keep borders closed, to protect children at school, to support those who need to self-isolate.

We need to support those who cannot afford vaccines or cannot afford to protect themselves, even globally.

We need to recognise that vaccine protection is something that can be gained, but also can be lost.

We are not fully safe, until we are all safe.

Exponential growth

Just compare the two pictures:

Fear over freedom: Here’s what the doom-laden government graphs didn’t show us (



Why these two figures? Trying to argue against – otherwise quite mild – restrictions implemented by the English government, The Telegraph is falling into an exponential growth fallacy, illustrated by the second figure.

The problem is of course associated with the different perceptions of the exponential growth, depending on the current level. But this attitude can be quite deceptive – as time goes on and the spread is not controlled, the numbers will start growing faster and faster. At some point, the epidemic will be unstoppable.

There is of course a way to avoid this problem with different perceptions at different stages of exponential growth. A logarithmic transformation turns exponential growth into a linear one, allowing the policymakers to make appropriate decisions.

The period from July 2020 onwards has three examples of exponential growth in the UK data, as illustrated above. At each time, the decision to respond has come late. It was quite clear that the numbers were growing exponentially even from late August 2020, but the decision to lockdown was only taken on 22nd September. The next wave started on 10th December, but the post-Christmas lockdown came on 26th December. The spread of the Delta strain became obvious from 19th May onwards. This time the government has only delayed the further relaxation, but no additional measures have so far been introduced to combat its spread in schools.

Essentially, the nature of virus spread is that any action to stop it needs to be implemented as early as possible. With the Delta strain of SARS-CoV-2 spreading exponentially in the UK we are probably already at the stage when it is becoming too late to stop the rapid pandemic spread.

It is true that the numbers are still much smaller than in March 2020 or January 2021. It is also true that with vaccination the growth will probably slow down soon and the epidemic will peak at lower numbers.

But it is also true that had we protected the borders, had we had a properly working test-trace-isolate system and had we acted earlier to prevent the spread, we could have avoided the illnesses and deaths of many people.

COVID-19 and trust

I think citizens have the right to express some unease at the way during a pandemic technology companies rode in to help governments all over the world, often free of charge, to collate and gain access to citizen data…

To beat a virus.

…with little scrutiny or oversight. Where was the vote, the public consultation in letting Amazon pair with the NHS, a private company, our health data? But that’s the point… isn’t it? …about algorithms. No one really knows how they work, even though in an increasingly automated world AI is making decisions for us all the time – what our insurance premiums should be, or A level results, or predictive policing, or even prison sentencing and release.

We know what you did during lockdown. An FT Film written by James Graham

A disturbing yet very wise film; we should all watch it.

But, instead of rejecting all lockdown restrictions and going down a rabbit hole of saying that all COVID19-related government actions are evil, we need to have a proper discussion of the balance between the private and public side of health-related behaviours.

I always thought of the lockdown measures as a covenant between the society (as represented by the government) and the individuals. In this covenant, we – as individuals – agree – temporarily and to a limited extent – to sacrifice our freedoms to save ourselves, our friends and relatives, and all others.

Why? Because we recognise that as individuals we are not always able to make the right decisions. We simply do not have all the information about the consequences of our actions, particularly during the pandemic.

It is the role of those in authority – be it the king (or the Queen), the Church, village elders, or the government, to control this balance.

We have been doing this for centuries.

But, the policy-makers need to be very clear why steps like hard lockdown, mask-wearing and track-and-trace – which James Graham is alluding to in this movie – are needed, how long they are there for, and what the exit strategy is.

During the pandemic, I have repeatedly said that I believe short and hard lockdowns, mask-wearing, wide vaccination, and border controls are needed to save lives and the economy.

But I also always said that the trust between the policy-makers and the individuals in the society must be there to successfully control the virus spread – successful control not only in terms of the virus suppression but also economic and societal costs and benefits.

I fear that this trust is missing across the globe. I fear that this is the reason why 100s of thousands of people have died and are dying unnecessarily early deaths. I fear this is the reason why we experience the biggest GDP slump since the 2nd World War. I fear this is why we see – and will continue to see – the repeated waves of epidemics and hard lockdowns desperately trying to save the health system.

I fear that the discussion about this COVID19 covenant is still missing and, more than that, the governments – and private companies – are going down the route illustrated in this film.