Risk Analysis of the Moderna and Pfizer Vaccines, conclusion

The bottom line

Taking all of the risks I determined / decided upon above, I put them into my spreadsheet, available here: Vaccine Risk Analysis.  I decided to calculate the risks for an average adult--meaning I don't use the average Infection Fatality Rate of 0.8%, which includes all of the vulnerable and elderly.  Instead, I put in an "individual fatality rate" of 0.1% for the purpose of the bottom line.  So this would be approximately the risk for a regular adult, not an elderly person.

I think it is worth looking at these "bottom-line" risks from two different aspects: relative risk and absolute risk.

Relative risk

 The question we are asking here is, "how many times more likely is it that something bad will happen to me if I decide not to take the vaccine, as opposed to taking the vaccine?"  The answer my assumptions produce is that there is roughly 16x the risk of death, 14x the risk of serious permanent injury, and 24x the risk of serious temporary injury.  This includes only the risk to oneself, not considering the risk to other people as well.

Note that this answer is not the answer to the question, "how much more risky is it to get Covid than to get the vaccine?"  I am including in the above risk factors the possibility that you will not get Covid at all even if you don't get vaccinated.  To get the comparative risk of getting the vaccine vs. getting Covid, you have to multiply all of those numbers by 7 or 8.  Oh, and in case it wasn't clear, the above multipliers also take into account the chance that you get the vaccine, but get Covid anyway and so have both the risks for the vaccine plus the risks for Covid (mitigated somewhat by the fact that the vaccine should reduce disease severity).

Absolute risk

The relative risk seems very clearly in favor of getting the vaccine, but it isn't the only important answer: we don't always care about relative risk.  After all, the risk of getting hit by lightning if you go hiking five times per year is about five times greater than the risk of getting hit by lightning if you go hiking only once per year, but we don't let that factor determine our vacation plans.  Five times a tiny risk is still discountable.  So what are the absolute risks here?

Again using the risk numbers for an average adult, I took the chances of a bad outcome for the "with vaccine" scenario and subtracted them from the chances of a bad outcome for the "without vaccine" scenario.  This gives us how much more likely a bad outcome is to happen if you forgo the vaccine compared to if you take it.

The results are that if you don't take the vaccine, your chance of death increases by 0.01%, your chance of serious personal injury increases by 0.06%, and your chance of serious temporary injury increases by 2%.  How significant these risks are will depend on your own personal risk toleration threshold, I suppose.

However, the absolute risk to other people must also be noted!  The chance that someone else will die because you forgo the vaccine is 0.3%, that someone else will suffer serious personal injury is 0.2%, and that someone else will suffer serious temporary injury is 5.5%.  Again, these chances would have to be multiplied by 7 or 8 if you wanted to know what the chances are to hurt someone else if you actually get Covid.

A 3 in 1000 chance of causing someone else's death, in my opinion, is a number that should give one pause.  It is, honestly, higher than I was initially expecting it would be and was one of the surprising things I discovered from doing this analysis.

How much stock should we put in these numbers?

It should be made quite clear that all of these numbers are ballpark estimates; the spreadsheet has all sorts of misleading significant figures in it, but that's just because it's formula based and those should all be ignored for the result portion.  I will note again here that I have biased my guesses in a number of places against the new vaccines; I have intentionally chosen what I considered worst-case scenario numbers for those risks, whereas I never did for the Covid risks.

It should also be made clear that the separate risk numbers are not all equally dependable.  In the case of fatality, we have a lot of hard numbers that can give us very reasonable estimates.  All of the online drama fighting over exactly what the IFR of Covid is and what exactly is a death "with" Covid instead of "from" Covid--that enters into these calculations as something that is at most about a factor of 1.5 or 2.  That barely matters for the sake of this analysis and it doesn't really change the bottom line at all.  I'm personally quite comfortable with the fatality risk numbers as good estimates.

In the case of the long-term risk, however, there was a lot more bald guesswork going on than with the fatality rates--both on the vaccine side and on the Covid side.  In this case, I still think it was a valuable exercise to go through and try to rate the risks as fairly as possible, but the end result should be treated as something like a Fermi Estimate (explained in this article: Fermi Estimates).  Fermi estimates have a long tradition in physics and have proven to be very useful in dealing with a lot of unknowns. With a Fermi estimate, you build up from a lot of informed guesswork (as I have attempted to do with these long-term risk estimates), and in the end, you hope your end result is accurate within an order of magnitude.  

On this basis, I think it's fair to say that my analysis indicates that getting Covid is roughly two orders of magnitude more dangerous than getting the new vaccine, and that since your chance to get Covid is roughly 10% if you don't get the vaccine, it's roughly 10x more dangerous not to get the vaccine than it is to get the vaccine.

I think this is a clear enough result that you can confidently base decisions on it.

Final words

Here at the end, I'd like to make one final point.  I think there is a category of risk that I have been completely ignoring that is worth discussing here, which is that if enough people decide not to take the vaccine, the pandemic could last considerably longer and more total people will eventually get infected.  I have been considering only the individual health risks so far, but there are serious societal risks as well.  There are many, many social evils associated with the pandemic continuing on for another year, or more.

I'm not here going to try to quantify these risks, and try to assign some portion of blame to an individual decision to not get vaccinated (like, maybe assign a fraction of a day of continuing societal ills to each decision?).  Firstly this is not appropriate because of how herd immunity works: you can tolerate a certain percentage of the population not being vaccinated and still get enough immunity to eliminate a disease.  Secondly, right now the vaccines are being applied as quickly as we can get them out the door, so this is a moot question.

However, if at some point the production and distribution of these vaccines outpaces the willingness of people to take them, then we will need to revisit this point.  I don't think anyone would argue with the extreme good of ending this pandemic as quickly as possible, and we need to realize that the vaccines are going to be the principle way in which we do that.