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Back to that Model (Modeling for dummies part 2)

May 14, 2020


Let’s pick up where we left off with the Modeling conversation. First, let’s remind ourselves of the three scenarios:

  • Scenario 1 = All the current positive cases are the total of all cases (meaning there are no asymptomatic cases and, therefore, we are not under-testing). So, in this scenario, the prevalence is 0.4%. This model predicts there will be about 15m deaths. NO WAY this is even close to the truth. It’s here for illustration purposes only. 

  • Scenario 2 = The prevalence is 5% (so we have about 10x-15x times more than the confirmed cases). This model predicts there will be a little over 1m deaths. This is, unfortunately, the direction we are headed unless dramatically different data on prevalence comes out, therapeutics have a breakthrough, or a vaccine becomes quickly available. 

  • Scenario 3 - The prevalence is 25%. We actually have a ginormous number of cases of which we are not aware. This model predicts there will be 250k death before we achieve herd immunity. 

I didn’t randomly choose prevalence as the variable to change. I chose it because it is the single variable that will have the most influence on the final death toll before herd immunity is achieved. 

If we never develop any good therapeutics or a vaccine whilst heading toward herd immunity, then social distancing will only affect the final number of deaths by making sure the demand for healthcare stays within healthcare’s capacity. This point is an important point. If you missed it, please re-read it.

Funnily, I listened to this after I wrote the above. He is saying essentially the exact same thing and did a very similar calculation to Scenario 2. He is just more eloquent. 

So here is the deal… 

  • if therapeutics are developed, then the case fatality drops for everyone who enjoys the benefits. 

  • if a vaccine is developed, then herd immunity occurs much faster and the people who obtain the vaccination will have a much, much, much lower risk of dying from COVID. 

You can now see how time comes into play. We can “alter” time by changing the Rt (or R0) (see R0 for dummies). Because the higher the Rt, the more people will get the illness sooner. As a result, fewer people will get the benefit of future therapeutics or a vaccine. There is built-in unfairness on whether you can work from home or not, your access to healthcare and so much else, but I digress.

Now, let's quickly turn the conversation back to the personal level from the population level. I’d like to challenge you to apply the Rt concept to yourself and your isolation group. How are you going to personally navigate the Dance? What is your personal case fatality rate? How important is the movement you need to do? What is your risk tolerance? 

We are nearing the end of this “for dummies” arc. We have talked about herd immunity, prevalence, R0, general mortality, personal mortality, and modeling and how all these concepts are intertwined. We have even touched on the concept of personal risk tolerance and trying to tease out the high and hinted at teasing out low transmission risk activities. Tomorrow I’m going to focus a lot more on this concept. Risks of activities are not binary. Getting drunk and driving on the highway at night during a snowstorm is different then sober day driving while wearing a seatbelt.  

Back to wrapping up the modeling conversation. So social distancing is a no brainer right? Well, not so fast. There are obvious disadvantages to strict social distancing. We have recently seen many of them. In one of my next “for dummies,” I will try to come up with a list of all the disadvantages of social distancing. It will be tricky as I will be venturing further away from my area of expertise - medicine. If you would like me to read and/or reference any stats or articles, I’m happy to read anything you send me. I need help here as I would like a comprehensive survey. 

As with many things in life, there will likely not be a “right “ answer. The Hammer was a no brainer. But, since my letter on April 14 entitled There are only hard questions left well... There are only hard questions left. It’s why I started this “for dummies” series a few days later. So, we can all understand the science behind what is happening. Then we can determine our personal paths during this insane time. 

Of course, if things get out of control again, our choices will need to again be dictated for us. Let’s not kid ourselves. If the healthcare system truly collapses everywhere, society will start to unravel. If things get out of control again, the Hammer should come out again. But, let's assume that doesn’t happen. Let’s assume we regulate the speed of the spread with personal decisions based on our own risk profiles and personal situations and thus, society develops an equilibrium of sorts as this pandemic makes its way through society. 

I personally will continue to talk to Adrienne about what we do as a nuclear family and continue to talk to my larger family and friend group often about how we should/could navigate this. I recommend you do too. Our ability to make personal choices on how we engage with Corona is being restored and so you need a plan. Don’t be a sheep. Make an intentional plan, whatever it may be. Hopefully, it is based on the best science we have to date. It will need to evolve as we learn more. 

I have learned a ton researching these “for dummies” letters. It is with this knowledge that I feel qualified to make the following recommendation on how we as a community, country, and world need to do the right type of Dance...

The Dance will need to be about maximizing all the population and personal health benefits of physical distancing while also maximizing the economic benefits of our distance-modified physical interactions. 

Interesting thought… I may have to change my salutation… but until then…

Stay socially connected and physically distant,


PS: A follow-up on the Skin Manifestation letter of COVID.