Natural Herd Immunity: 10 questions to No 10’s experts danielequercia Follow Mar 14 · 6 min read

Yesterday at least three government advisers (experts) went on TV to advocate for “natural herd immunity”, which translates into a “do nearly nothing for now” strategy. To put it simply, the goal is for 60% of the UK to become infected in order to develop “natural herd immunity” against COVID-19.

My opinion is that talking about “herd immunity” in this context is simply “science fiction”, not least because: 1) we do not have a vaccine, and 2) we do not know if recovering gives immunity. As the Head of WHO puts it, we know very little about this virus. Plus, I find the value system behind the proposal of “natural herd immunity” to be horrifying. Finally, we should see things into the broader context: I think the UK government is using this strategy as a “delay tactic” to then blame “the scientists” (or science) when it will not work. Discrediting science is a political strategy. But that’s an opinion (with some recent supporting evidence in UK and US).

What bothered me the most, however, was that, being a scientist myself and knowing the limitations of scientific modelling, I could not believe that these experts were blindly trusting their models so much so to advocate for roughly 40 million people to catch COVID-19 (which, even with a fatality rate of even 1 means 400,000 dead). I started to wonder why they did so. To be charitable, they might have done so because they were on TV — it’s the medium’s fault not the messenger’s. However, I’m bothered by the fact that such a TV-induced simplification might result in more than 400,000 deaths in this country — the country in which I live. After all, the 1s/0s in their models are human beings, and only those with psychopathic tendencies would sacrifice human lives based on unreliable modelling, and scientists are not psychopaths (or, at least, I’d like to believe we are not). As scientists, we need to be humble and always state the assumptions our models make, especially if we are going on TV to communicate complex and difficult policies. The so-called experts should embrace complexity by conceding that they understand only a tiny part of the problem.

Models are simplified versions of reality and, as such, make simplifying assumptions. Reality is more complex. To tackle a problem in a complex system (our society is a complex socio-technical system), one does not usually have a “unique winning strategy” and often resorts to a family of strategies (always keeping in mind that the effects of the implemented strategies are hard to control, given the limited “controllability” of complex systems). Yet, all three experts ignored that complexity and repeatedly said that: a) There is only one strategy; and b) That strategy is “natural herd immunity”. Please see for yourself whether I’m misrepresenting their positions.

Expert #1 The government’s chief scientific adviser Patrick Vallance (@uksciencechief), March 13th. A former researcher in vascular biology who took R&D positions in a major pharmaceutical company. Not specialised in Public Health.

Expert #2 Prof Graham Medley @GrahamMedley of @LSHTM, March 13th. A self-proclaimed “simple modeller” who was happy to go on TV advocating for a “natural herd immunity” strategy without stating the simplifying assumptions his models made. He explained how a “nice big epidemic” works, was quick to point out the shortcomings of other models (e.g., he explained why “social distancing models” do not work as they don’t account for contacts at home), but failed to mention the assumptions behind his models (which we should think are nearly perfect and conclusively support the “natural herd immunity” argument).

Expert #3 Prof John Edmunds (again of @LSHTM), March 13th. He can see only one way forward — that is, achieving “natural herd immunity” by infecting 60% of the UK — there is “no way out of that”, he added.

Before going on TV to support a single-solution answer, these experts should have paused a bit and considered the complexity of the issue. I have 10 questions for them:

1. Are your models & data publicly available? Transparency is key, especially in public policy. At the moment, your models are self-reviewed and not peer-reviewed. There cannot be a scientific debate if other scientists do not have access to your models and data.That’s how science works, and that’s how you gain public trust.

2. What’s the NHS capacity your models assume? Your models work only if you make provision for the critically ill. What is the assumed availability of ICUs? Did you account for the fact that hospitals might be overwhelmed with secondary deaths? What happens to blood donations? What happens to patients going to get their regular cancer treatments? It is very likely that NHS will not cope with your “natural herd immunity” strategy.

3. Do your models assume “no reinfection” in the long term? Or, at least, you should have said that your models make an assumption for which there is currently no supportive and conclusive evidence (and there is plenty of misinformation on the subject matter).

4. In public policy terms, is it honest to say the 1s/0s in your models really mean “(not) being immune”? Is immunity an honest word in this case? It is fair to say those who recover are NOT permanently in the SAME condition as those who never got the virus (which the word “immunity” wrongly suggests). The immunity you are talking about is not that coming from a vaccine but is that coming from recovering, and those who recover can be left with reduced lung function. Given the proposed 60% figure, this is a massive social experiment.

5. How the availability of a vaccine (in 18 months) would change your models’ results? Do we really need to sacrifice 1/2 M people now? Or is there any alternative that would allow for a delay? How about massive testing? What’s wrong with this 3-step process: 1. Delay the spread; 2. Let the scientists develop a vaccine; 3. When the vulnerable are at less risk, develop herd immunity.

6. To which extent the government’s lack of testing has an effect on your strategy? In combination with your idea of natural herd immunity, the government has decided to stop testing. Has that no impact in the ability of your models to adjust to changing circumstances? Does your “natural herd immunity” strategy work in the absence of testing? It is hard for me to understand how we develop “herd immunity” if we are not testing. If don’t test, how can people return to work, for example?

7. Can you assume that the vulnerable will be protected? A central assumption of your “herd immunity” plan is that you can identify the 40% you wish to save, and that you actually save them. Well, that’s a big assumption. If the type of people getting sick are not the right ones, your model fails. Even assuming you successfully identify them, what’s the plan? Isolating them at home? Is that reasonable to assume given the (family?) support system in England? Are we going to ship them to Scotland? In this interview, the governmental Nudge Unit was proposing “cocooning”. It’s your duty to at least outline a plan. Your model is as credible as its assumptions.

8. What’s wrong with temporary social distancing strategies? They would avoid NHS to collapse.

9. How can you control a complex system? Your strategy assumes that you can control (fine tune) the infection rates. How would you do that in the presence of a variety of human behaviours? Or in the presence of exogenous events in a fully interconnected world?

10. Are you unwittingly part of a political strategy to discredit science? TV and social media are powerful amplifiers, and your message is part of the context, including the political context. In his press conference, the PM said that the decision was based on science, and he said so many times. Then you went on TV to defend this single-answer policy. That is not a coincidence.

Looking forward to your answers.