Why herd immunity is not an option for the UK as it faces Covid-19

With less than 10 per cent of the UK population presumed immune, thousands of deaths will result without new rules. 

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In January, when the New Statesman first asked my opinion on the respiratory virus identified in Wuhan, I was struck by the seriousness with which the Chinese were treating the outbreak. How do you close a city of around 11 million people? But China had experienced a previous Sars coronavirus outbreak in 2003, and epidemiologists had long feared the emergence of a hyper-virulent, easily transmitted virus. Was this it?

By February, terrifying scenes emerged from northern Italy; dying patients crammed into hospital corridors with overworked doctors succumbing alongside them. By early March, cases were spreading predictably in the UK, where any opportunity to prepare had been squandered. I was among those calling for a lockdown and was surprised by the criticism I received over my “alarmism”. With no vaccines, no drugs, inadequate capacity in intensive care units and a shocking lack of ventilators, what other options were there?

On the day of lockdown on 23 March, the UK reported around 500 positive cases. Because testing was so limited, the true number infected was perhaps 20 or 30 times higher (around 15,000 infections). The deaths were easier to count; 55 people died that day.

On Thursday of this week (8 October), now with a comparatively robust testing system, the UK reported 17,540 cases with 77 deaths. In March, it was getting warmer and sunnier. Now, it is getting colder. We’re heading into the winter months, during which –even in a normal year – thousands are hospitalised with colds and flu.

Should we lock down again? The economic devastation, and impending health crises of missed diagnoses and lost treatment for non-Covid-19 disease make this a difficult call. We know enough about the virus to negate the need for a lockdown, but the question is whether we can effectively use that knowledge.

China shut down fast, tested on a vast scale after re-opening and hit the disease hard with localised lockdowns. It has effectively controlled Covid-19. New Zealand closed its borders and aggressively tested, traced and isolated cases; Covid has claimed only 25 lives there. South Korea led the way with a ready-to-go test and trace system, employing policies designed in response to the Sars epidemic of 2003 and a Middle Eastern respiratory syndrome (Mers) coronavirus outbreak in 2015. The country's death toll is 1 per cent of the UK's. Sweden’s well-known policy of responsible social distancing avoided lockdown and, in spite of criticism, they have done comparatively better than the UK.

Even now, fewer than half of Britons voluntarily self-isolate if they show Covid-19 symptoms. The ad-hoc route to tracing contacts makes a mockery of the system. Only since late September has it been a criminal offence to fail to isolate. It seems barely a day goes by without a public figure being admonished (but seldom punished) for dodging the rules, reinforcing the feeling that this is not that serious.

If everyone wore a face mask at all times when around other people, this alone would allow the R0 value (reflecting the number of people to whom one infected person will transmit the disease) to drop below 1, driving the disease to elimination. Compliance with distancing measures should be enough to prevent a new lockdown. Covid-19 control needs as much sociology as virology.

Other things have changed since March, too. Increased ventilator numbers and the ability of the Nightingale hospitals to fire up again at short notice will help. Personal protective equipment is more widely available for medical workers, significant numbers of whom, having already been infected, will also be protected by acquired immunity. The public health catastrophe of discharging elderly patients from hospitals into care homes must not be repeated and extra efforts to shield vulnerable communities must be taken.

Treatment has also improved, although most people will not be able to access the kind of medical intervention that served Donald Trump well last week. The drugs from which he benefited included Remdesivir, an anti-viral agent that slows replication of coronavirus, that must be given by intravenous injection over five days. It costs thousands of pounds for each course of treatment. The Regeneron antibody cocktail isn’t even licensed for use against Covid-19, and monoclonal antibody therapies such as this are notoriously expensive.

Convalescent antisera, which contains antibodies from recovering patients, can be used to combat the virus in others. But the logistics of harvesting these antibodies will struggle to keep pace with need, and evidence for their use is not strong anyway. Even dexamethasone, a relatively inexpensive anti-inflammatory drug that diminishes fatality rates in the seriously ill, might not be available on the scale needed during an uncontrolled outbreak this winter.

I’ve grown increasingly confident that a vaccine will be achieved, as the SARS-CoV-2 coronavirus does not suffer the confounding issues of strain variation and high mutation rates that have thwarted efforts to make vaccines against many other pathogens. Several of the novel technologies that have enabled the development of Covid-19 vaccines in record time do trigger people to produce anti-coronavirus immune responses. Even partially efficacious vaccines would help tip R0 below 1. However, even if successful, the production and distribution of a new treatment for the entire country poses formidable challenges. And there is no prospect of a vaccine being available for use against a rapidly growing second wave this winter.

That leaves us, therefore, with a stark choice. Strict adherence, through enforcement if needed, to distancing rules, or else a second lockdown. With less than 10 per cent of the UK population presumed immune following infection, the alternative – allowing “nature to take its course” – will result in many thousands of deaths.

Michael Barrett is professor of biochemical parasitology at the University of Glasgow

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