Evidence Fiasco

With a boulder on my shoulder
Feeling kinda older
I tripped a merry-go-round
With this very unpleasing
Sneezing and wheezing
The calliope crashed to the ground
--Manfred Mann's Earth Band

A Stanford MD and professor of biomedicine discusses the 'evidence fiasco' associated with the COVID-19 pandemic. His central premise is that we lack essential data on infection rates that enables effective decision-making. Draconian countermeasures adopted by many countries may be doing more harm than good.

As these pages have suggested, extant data on number of people infected and how the epidemic is spreading are unreliable. Limited testing underestimates the positive case count; number of true infections may differ from counted cases by orders of magnitude. Three months after the virus outbreak, no country has reliable data on the prevalence of the virus in a representative sample of the general population.

That is mind numbing.

The evidence fiasco creates extreme uncertainty about predicting how many will die from COVID-19 because case fatality rates are meaningless when selection bias causes patients with disproportionately severe symptoms and bad outcomes to be tested. Currently, reported death rates from positive cases are far higher than they would be if more tests were administered (the denominator in # deaths/# total cases goes up).

The author suggests that the Diamond Princess cruise ship situation presents an interesting example of a single, closed population where all of its and passengers were quarantined and tested for COVID-19. The author does not include all of the data in his discussion, so I am drawing from reports here. About 3,400 crew and passengers were quarantined on the ship off the coast of Japan for about two weeks. During that time, 696 tested positive for an infection rate of 20%. Of those cases, 410 (59%) were asymptomatic. Seven deaths were attributed to COVID-19, translating into a 1% case mortality rate and a 0.2% death rate for the population. It is also important to note that this population was skewed disproportionately toward elderly people who are much more susceptible to severe COVID-19 effects.

Projecting the Diamond Princess mortality rate onto the age structure of the US population, the author estimates the death rate among people infected with COVID-19 to be 0.125%. However, because the small sample size widens statistical confidence intervals, he estimates that the true death rate ranges from five times lower (0.025%) to five times higher (0.625%). If other uncertainty factors, such as frequency of chronic diseases for tourists and the possibility that some infected passengers in the sample might die after the quarantine period ended, then a reasonable case fatality ratio estimated from the Diamond Princess situation might vary from 0.05% to 1% for the US population at large.

The results suggest a large range of severity possibilities associated with this pandemic. If the true population fatality rate is indeed close to 0.05%, then it would be lower than the seasonal influenza death rate. Locking down the world based on such a death rate would be completely irrational given the economic, financial, and social consequences associated with this countermeasure. Indeed, concerns that the lock down approach constitutes an overreaction to the COVID-19 pandemic are increasingly being raised.

The author's recommendation is straightforward. The best information for good judgment here comes from data on exact levels and trends in prevalence and incidence of epidemic activity. Prevalence of the infection can be understood by testing a random sample of the population for the presence of the COVID-19 virus. I would think tagging those cases as symptomatic/asymptomatic would add further utility. Incidence of the infection can be understood by repeating the exercise at regular intervals to estimate the rate of new infections.

Meanwhile we are making decisions that cost trillions of dollars without the benefit of essential information, which raises the probability that current measures to counter the pandemic will be worse than the disease itself.