There is no ‘scientific divide’ over herd immunity

Marco Bottigelli via Getty Images / WIRED

On October 4, in a wood-panelled room at an event hosted by a libertarian think tank, three scientists signed a document that they say offers an alternative way of responding to the Covid-19 pandemic. The signing of this so-called “Great Barrington Declaration” was greeted with clinking champagne glasses before the signatories jetted off to Washington DC on the invite of White House coronavirus advisor Scott Atlas.
Aside from the three lead signatories, there is little about the Great Barrington Declaration that feels convincingly scientific. Not its website, which boasts that the statement has been signed by 2,780 “Medical and Public Health Scientists” who only had to tick a box and enter a name to be included on that list. Nor the brief declaration itself, which offers little in the way of scientific evidence or even substantially new policy suggestions.

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While the science isn’t particularly convincing, the Great Barrington Declaration has been successful in one respect. It suggests that scientists fall into two camps: those who are pro-lockdown and those who think we should avoid lockdowns and allow people to become infected, hopefully building up enough herd immunity along the way. The media has picked up on this narrative of a supposed rift among scientists and has run with it, while simultaneously declaring that no one is talking about it. “[The Great Barrington Declaration] has been almost entirely ignored by the media outlets that spend much of their days presenting themselves as obedient to science,” wrote James Freeman in the Wall Street Journal on October 6, the same day that stories about the statement ran in The Guardian, Independent and Telegraph and ignoring the fact that articles about this supposed divide have been bubbling along for almost as long as the pandemic.
So how much of a divide is there? Let’s leave to one side the fact – as Christina Pagel, director of University College London’s Clinical Operational Research Unit noted on Twitter – that almost every single major medical body is on the “side” of not allowing Covid-19 to run unrestrained through young people. Instead, let’s look at the substance of the Great Barrington Declaration itself.
The gist of the declaration is this: lockdown policies have significant negative effects on other health outcomes, and so governments should pursue a strategy that the signatories call Focused Protection – shielding vulnerable people from infection while letting the virus romp through the rest of the population.
On the first point, the signatories are absolutely right. We know that lockdowns disrupt cancer care and other health services, and have a significant negative impact on mental health. No one wants those outcomes. “Current lockdown policies are producing devastating effects on short and long-term public health,” the authors write. And they’re correct. Almost.

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The problem is that we aren’t in lockdown. Across the UK, pubs, restaurants, schools and universities are all largely open. The kind of lockdown that the Great Barrington Declaration seems to be railing against hasn’t been in place in the UK since mid-June. Even in places like Manchester which are under local lockdown restrictions, pubs, restaurants and schools are still open and it’s hard to find people who are advocating for a return to the lockdown we saw in March. When the Great Barrington Declaration authors declare their opposition to lockdowns, they are quite literally arguing with the past.
So what do the Great Barrington Declaration authors suggest we should be doing? “Simple hygiene measures, such as hand washing and staying home when sick should be practiced by everyone to reduce the herd immunity threshold. Schools and universities should be open for in-person teaching. Extracurricular activities, such as sports, should be resumed. Young low-risk adults should work normally, rather than from home. Restaurants and other businesses should open,” they write. Sound familiar? These are – more or less – the policies that the UK government has been following since September, with the exception that the government advice changed in mid-September that people should work from home if they can.
What is more interesting about the Great Barrington Declaration is what is missing. There is nothing about test and trace or mask-wearing – two interventions that we know are effective at stopping the spread of Covid-19 and don’t require any curtailing of our individual behaviour. It’s not clear why these are absent from this plan, but it might be because they would slow the spread of the virus, while the authors of the declaration generally advocate that slowing the spread upon less vulnerable populations is not necessary, as long as vulnerable people are shielded.
This is where things start to feel really wobbly. For a start, we don’t know enough about Covid-19 immunity to say that having the disease does offer long-term protection. But even more crucially it’s not clear who exactly the authors mean by “vulnerable”. Yes, older people are at a significantly higher risk of getting seriously ill or dying after contracting Covid-19, but the illness has a very serious impact on people across all age ranges. Just ask the people who are suffering months after initially falling ill with the lingering symptoms of Long Covid. Are they vulnerable?

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Yet the authors don’t offer us any way of categorising vulnerable or non-vulnerable people. Many scientists have pointed out that completely shielding vulnerable people is practically impossible, but the Great Barrington Declaration authors don’t even make an effort to indicate how this shielding might work. In a video interview with UnHerd, Jay Bhattacharya a professor at Stanford University Medical School and one of the declaration’s authors, struggled to explain how a school age child living with a grandparent should actually change their behaviour to protect people.
It seems fairly obvious that no government could effectively seal off every single vulnerable person in a given population, yet the Great Barrington Declaration signatories don’t indicate how the impact of the disease will change depending on the level of shielding achieved. Researchers at the Max Planck Institute in Germany have, however, and they concluded that long-term shielding would be impossible for a number of reasons outlined here.
But the media reports about this great “scientific divide” are right about one thing. The lead signatories are prominent, successful scientists. Martin Kulldorff is a professor of medicine at Harvard University, Sunetra Gupta a professor at Oxford University and Jay Bhattacharay a professor at Stanford University Medical School. So why are they relying on press releases and champagne-clinking events with libertarian think tanks rather than following the scientific method of testing their hypotheses in a rigorous way and publishing their findings for critique?
A quick look at the preprint server medRxiv shows that these three lead signatories have been publishing papers related to Covid-19, but they haven’t – to the best of my knowledge – published any modelling that puts their shielding theory to the test. In May, Gupta published a study suggesting that coronavirus may have infected half of the UK population already. She was wrong – in London the proportion of those infected seems to be close to 18 per cent – but that’s how science works. You allow your results to be scrutinised, you adjust and you try and get closer to the truth next time. With this declaration, the three lead signatories are positioning themselves on one side of a manufactured scientific debate, but they’re not putting the science front and centre at all.
On Twitter, the economist and statistician Tim Harford noted the “scientists divided” theme featured prominently in the campaigns of tobacco firms keen to delay action on smoking-related disease and climate change deniers. We should be careful about how we interpret any so-called divide when it comes to Covid-19. And when we’re weighing up whether one approach is better than another, we should be extremely clear about what is science, what is supposition and what is just surface.
Matt Reynolds is WIRED’s science editor. He tweets from @mattsreynolds1
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