Get them all!

The siren song of collective immunity.

Sep 26, 2020

This one’s a bit of a doozy but bear with me. You’ll want to know this stuff as we hunker down for a second (or ongoing first) wave.

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“Letting the virus run its course” is not science; it’s lazy governance

A casual observer might deduce that, though they’re not just coming out and saying it out loud, some governments’ policy is to let the virus run amok amongst their strongest citizens, relying on personal behaviour to protect the most vulnerable, so as to reach the El Dorado of herd mentality. I mean immunity.

1. What’s herd immunity?

Herd — or group, or collective — immunity is when enough individuals carry antibodies against a pathogen that they can act as a barrier against, rather than vectors for, it. These defences must last for it to be reliable. Herd immunity is what we aim for when we launch mass vaccination campaigns. It is a threshold expressed as a percentage, and it changes depending on how contagious the illness is. For measles, 93% to 95% of the population must be immunised. For polio, we look for 80% to 85%.

In the case of Covid-19, scientists estimate the threshold is around 65% to 70%. This means at least two out of three people must develop durable, effective antibodies to protect the whole of the population.

2. So how do you get antibodies?

Your body must be exposed to a pathogen so as to learn about it and drum up an army to fight it. You do that either by getting sick or vaccinated.

We don’t have a vaccine, obviously. So the logic of herd-immunity seekers goes as follows: enough strong, healthy people should get sick and recover so we can move on. We’d be sure to protect the most fragile amongst us, of course, and accept as inevitable and necessary whatever losses we might sustain. Let the olds take one for the team!

3. Well, should we not?

The scientific consensus is — and I cannot stress this enough — hell no. The idea of letting the virus run its course is not just unacceptable from an ethical perspective (I prefer the term “criminal,” but I’m emotional), it’s also unscientific:

In the public health community, there is an almost unanimous consensus: that COVID-19 is a serious illness with high infectivity and mortality. Certain groups are more at risk from it (such as older people) but none are spared by it. A significant subset of people develop chronic complications of the infection and it is still unclear if it confers long-term immunity in most people. Managing this pandemic requires either a suppression strategy, with restrictions and mitigatory measures, or an elimination strategy.

The first reason for this is that we have no idea how long immunity lasts after infection. Typically for a coronavirus, based on the strains we already know, the immunity lasts from 12 weeks to about a year. It’s only been a few months of this nightmare, so data are limited. As you may remember, new studies have been encouraging, but there also have been a few reported cases of reinfection. We just don’t really know what we’re dealing with yet.

The second reason is that the notion we can both let the virus go nuts AND protect the vulnerable is a delusion. You cannot isolate the elderly and the immunocompromised without harming both their mental and physical health. And even if you could, it’s just not feasible. Our lives are too interdependent. We’ve seen this scenario happen repeatedly:

From June through August, the incidence of the virus was highest among adults ages 20 to 29, according to research published on Wednesday by the Centers for Disease Control and Prevention. Young adults accounted for more than 20 percent of all confirmed cases.
But the infections didn’t stop with them, the researchers found: Young adults may have also seeded waves of new infections among the middle-aged, and then in older Americans.

The same thing happened in France. When the second wave began to accelerate over the summer, it was mostly amongst young adults. This, in fact, was the main argument people gave me when I asked them to be more careful. “It’s ok, it’s only young people,” like a broken record. It would be, of course, a matter of time until their mums and dads and grannies and grandpas began to fall ill. As I write this, two out of three people hospitalised in France are more than 65 years old.

Incidentally, French researchers have estimated that the proportion of the population with antibodies was around 6% at the end of the spring. They also calculated then that to reach full herd immunity, more than 355,000 people would have to die (probably less now that we know a bit better how to prevent deaths, but you get the gist).

To say that letting Covid-19 run wild would create a global catastrophe of historic proportions is an understatement. Even by 2020 standards.

4. But Sweden…

Sweden more or less openly followed what I will now refer to as the Lazy Bum Strategy. Besides the fact that they experienced the highest death rate amongst comparable nations, was this effective? Did they, in fact, reach herd immunity?

Anders Tegnell, Sweden’s top epidemiologist, estimated that infected people in Stockholm would reach 40% of its population in May. For the country as a whole, he said this number would be 30%.

Even with these numbers, you’re far below the threshold for Covid-19 herd immunity, but then two studies contradicted Tegnell’s estimates. They found that Stockholm was at 17% in April (similar to London, which was locked down) and the whole of Sweden at 6% in May.

The Swedes were not remotely close to herd immunity. They eventually implemented soft restrictions, which they maintained all through summer and which slowed down the spread of the illness considerably, so it is still not likely that they’re collectively protected.

As kids return to school and people head back indoors, most experts are bracing for a new wave. There’s already been an uptick.

5. New York City, then…

Still no. They think 22% of us in NYC were infected in the spring. It’s a lot, but it’s not enough, not by a long shot. You know what, I’ll just let Anthony Fauci take this one:

6. But the economy…

Most economists will stop you right there. “Public health or the economy” is a false dichotomy. Now a majority of experts agree that the only way to salvage economic growth is to suppress or eliminate the virus:

Out of those surveyed, 74 percent of economists said the U.S. would be in a better economic position now if lockdowns had been more aggressive at the beginning of the crisis. Among that camp, the most commonly cited reason was that early control over the virus would have allowed a smoother and more comprehensive return to economic activity later on. “More aggressive lockdowns would have [gotten] the country in a better position (health wise) as we head into fall and winter,” said Andrew Patton, a professor of economics and finance at Duke University.

This isn’t just an opinion, mind you. It’s been borne out by the evidence. Lockdown or no lockdown, the economy would’ve ground to a halt in the U.S.:

Goolsbee and Syverson found total consumer traffic fell by 60 percentage points, but legal restrictions accounted for just 7 percentage points of this. That is, it caused less than 12% of the total effect.

The lesson is that it is more advisable to do a well-coordinated, aggressive lockdown to hammer the pandemic on the head, with clear guidelines for all to follow uniformly. The sooner you do it, the sooner you can focus on recovery.

How to use this: it’s very easy to get confused. Those advocating for herd immunity before a vaccine is available may sound very serious and scientific, and they may be given a platform by many media outlets, but public health specialists in the U.K. have likened this to falsely “balanced” reporting on climate change. There is no real debate about this. We should demand more from our authorities.

The outsized role of structural factors and luck

Those who know me know I’m always advocating for a comparative approach to self-knowledge. The method helps us identify the lessons others have learnt so that we may improve upon them, as well as the way in which we differ from others, and why solutions that work for others may not work for us.

Now I’m seeing some of these conversations happen as we evaluate how we’ve fared in the past six months. Many post-mortems (pardon the grim choice of words) are made in absolute terms, looking exclusively at what localities did. When you look at it comparatively, however, you realise how much is out of our control, and that pre-existing structural factors, as well as luck, play a huge role.

In that spirit, let’s look at Sweden again: the fact remains that even without harsh restrictions, they kept a lid on infections. Why? The explanation may well be structural. We know from studies that the virus being passed amongst household members accounts for 20% to 50% of all infections — the biggest risk to us is someone we live with. In Sweden, households are really really small (2.2 people; consider this against the OECD average of 2.63). That would be protective.

Two days ago SFGate ran a self-congratulatory piece on how San Francisco did during this pandemic:

"The low case rate is a result of people acting well, and acting well is everything from city health leaders doing the right thing to the people doing the right thing," said Dr. Bob Wachter, chair of the Department of Medicine at UCSF. "We have very high rates of mask-wearing, probably the highest in the country. I think from the beginning people have trusted the science, trusted the guidance. You don’t hear in S.F. that COVID is a hoax. People have generally taken this very seriously and I think the leadership from the mayor and the regional health directors has been terrific."

It is true they reacted quickly and did their best to stick to the science. But can that account entirely for their success?

We live in NYC, and unlike many families, we haven’t left. Schools shut down on March 13th, the mask mandate was implemented in April. Still, we’ve endured the largest losses of any city in the world, tallying up nearly the same number of deaths as the whole of France in the same period. We sent refrigerated trucks to relieve our morgues and dug mass graves for our fellow New Yorkers. You’ll never hear anyone argue that Covid is a hoax here, either.

One factor was that the virus was circulating in NYC long before state and federal governments recognised the emergency. In SF, it started long after they rang the alarm. That’s luck. Another element is the demographics. SF’s 900,000 population counts no more than 13% of Black people and non-white Latinos, whilst they represent nearly 30% of our 8.4-million-people metropolis. In SF, the average household size is of 2.3 people. In NYC, it’s 2.4, a number that shoots up for Latinos (2.7).

It is true that SF’s population is far healthier on average than most. In the U.S., health is closely related to income. The median income in SF is about $96,000 per year, whilst in NYC is it $63,000. Not to mention the fact that NYC counts one hospital for 135,000 people, whilst in SF you have one hospital for 43,000.

How to use this: before you start advocating for measures implemented successfully elsewhere, look at the underlying structure they were working with, and compare it to the one where you live.

Generally speaking, just remember to think critically. When you’re not sure, dig deep. This, after all, is a disinformation pandemic as well.