Sunday, 30 August 2020

A primer on herd immunity for Social Darwinists

Herd immunity has been proposed as a way to deal with the new Corona virus. In the best case, it is a call to slow down the spread of the SARS-CoV-2 virus enough so that the hospitals can just handle the flood of patients, in the worst case it is a fancy term for just doing nothing and let everyone get sick. 

Trump often talked about letting the pandemic wash over America. Insider reports confirm he was indeed talking about herd immunity. When I first heard claims that Boris Johnson was pursuing herd immunity, I assumed his political opponents were smearing him and trying to get him to act, but it seems as if this was really his plan. Of all world leaders Jair Bolsonaro may be most in denial about the pandemic, which he calls a little flu. He also advocated herd immunity. All these leaders have downplayed the threat, which by itself helps spread the decease, and advocated policies that promote infection, leading to more infected, sick and dead people.

America and Brazil lead the COVID-19 death rankings unchallenged with respectively 187 and 120 thousand total deaths and around one thousand people dying every day the last month. The UK is the country with the most COVID-19 deaths in Europe, while it was lucky to get it late.

This "strategy" has a certain popularity among Trump-like politicians. I do not think they know what they are doing. Scientific advice tends to come from a humanist perspective where every life is valued. Such advice is naturally rejected by Social Darwinians, who in the best case do not care about most people. While these politicians naturally see themselves as more valuable than us, they tend not to excel in academics. So let me explain why herd immunity is also a bad policy from their perspective, even if up to now people from groups they hate had a higher risk of dying.

Herd immunity

If we do not take any preventative measures one SARS-CoV-2 infected person infects two or three further people. This may not sound like much, but this is an example of exponential growth. It is the same situation of the craftsman who "only" asks the king for rice as payment for his chessboard: one grain on the first square, two on the second, four on the third square and so on.

If we assume that one person only infects two other people, that is that the base reproduction number is two, then the sequence is: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, ...
536,870,912, ...

Those are just 30 steps to get to half a billion and the steps take about 5 days in case of SARS-CoV-2. So that is half a year. With good care 1 to 2 percent of people die, that would be at this point 5 to 10 million people. Do be highly optimistic and it is still 2 million people.

Much more people need to got the hospital. In Germany this is 17%. A recent French study reported that after 110 day most patients are still tired and have trouble breathing, many did not yet work again. That would be around 200 million people with long-lasting health problems.

This will naturally not happen in reality. People will take action to reduce the reproduction number, whether the government mandates it or not. And at a certain moment an infected person will not infect as many people because many are already immune. If the base reproduction number is two and half the population is immune, the infected person will only infect one other person, that is the effective reproduction number is one.

The actual base reproduction number is most likely larger than two and reality is more complicated, so experts estimates that the actual herd immunity level is not 50%, but between 60 and 70%. More complication is that it is possible that people are sufficiently immune to avoid getting ill again, but the immunity may not prevent people from getting infected and transmitting the virus. There is a strong case of a 33 year old man from Hong Kong, who got infected twice, but did not get ill. If this were typical, herd immunity would not exist.

You may have heard experts say that once this immunity level has been reached, that the pandemic is over. But this does not mean that the virus is gone. Europe needed several months of an effective reproduction number well below one to get to low infection numbers (and the virus is still not gone). This was after a drastic decrease in the effective reproduction number (R) due to public health measures, in case of herd immunity it would initially be around one, and only very slowly go below one.

Say that when we reach R = 1 when one million people are infected, the after one step later (5 days) another one million people are infected. One million of 30% of the world population is not much. So also R will still be almost one. In other words, it would take several years for the virus to go away even in the best case. In the worst case, the virus mutates, people lose some immunity and new babies are immunologically naive. So most likely SARS-CoV-2 would stay with us forever.

Reaching herd immunity will not help Trump. He will still be bunkered down in the White House surrounded by staff that is tested every day so as not to infect him, while the calls on others do go out, without a good testing system, and die for him. Trump's billionaire buddies will still need to lock themselves up in their mansions or high-sea yachts, counting how much richer they got from Trump's COVID-19 bailout. The millionaire hosts at Fox News will stay at home telling others to go out to work even if their work place is not safe and to accelerate the pandemic by sending kids to schools even it the schools are not safe. They will still need to wait until there is a vaccine. The herd immunity strategy only ensures that up to that time the largest number of people have died.

When the virus is everywhere, good luck trying to keep it out of elderly homes. In 2016 Trump won in the age groups above 50. The UK Conservatives had a 47 point lead among those aged 65+. In Brazil Bolsonaro had a 16 percent point lead for people older than 60. They will be the ones dying and seeing their friends die. This is not helpful for the popular support of far right politicians.

The elite may think that it will be the poorest 70% that get infected. Far right Republicans may hope that it will affect Democrats and people of color more. It is true that at the moment poor people are more affected as they cannot afford staying at home even if their place of work is not safe. It is true that initially mostly blue states and cities were affected in America.

Let's take the theoretical case where the poorest 70% are infected or immune and the richest 30% still immunologically naive. As soon as one of these 30% are infected, it will spread like wild fire as rich people tend to hang out with rich people, so the virus would easily find two or three rich people to infect next.

That is one reason why it is too simple to equate a base reproduction number with a herd immunity of 50%. This would be the case if the population were perfectly mixed. But any network were the immunity level is not yet 50% is up for grabs. In the end everyone will get it, rich or poor, red or blue.

The only Social Darwinists for whom this pays are billionaires who have their own private hospital, with their own nurses, doctors at their mansion. They would have a chance of 1 to 2 percent to die. While if they manage to convince the people to go for herd immunity and not even to stay below the carrying capacity of the hospitals around 5% of the population would die. That is a 2 to 3% survival difference. Not sure that is worth getting all your politicians kicked out of office.

It naturally also helps the high frequency traders. Like the Mercer family who funded Trump in 2016 when no one thought he was a good investment. They have made so much money from the chaos Trump produces. Up or down the high frequency trader wins. Down goes faster. They live their lives on chaos, suffering and destruction. I presume they have a private hospital, they have the money.

But for the average Joe Social Darwinist there are nearly no gains and it is bad politics. It hurts your country compared to more social democratic countries and at home it helps lefties get into power and implement disgusting policies that help everyone.

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