An inability to understand numbers may be why COVID continues to spread
Question 1
A virus is circulating. The number of infections in a month rises 25 percent from January to February, then drops 25 percent from February to March. Is the number of infections in March (a) larger than the number in January, (b) smaller than in January, or (c) the same as in January?
Question 2
Two viruses are circulating, Epsilon and Upsilon. Epsilon’s case fatality rate is twice as high as Upsilon’s, but Upsilon is twice as transmissible. Other things being equal, which virus will kill more people: (a) Epsilon, (b) Upsilon, or (c) no difference?
Question 3
Jamie and Lauren are both vaccinated against a virus. The vaccine is 90 percent effective. Jamie lives in a community where 80 percent of residents are vaccinated, while in Lauren’s similarly sized community only 40 percent are vaccinated. Who is more likely to become infected: (a) Jamie, (b) Lauren, or (c) no difference?
Question 1 answer is B
The decrease more than offsets the increase because it is 25 percent of a larger number.
Question 2 answer is B
The effect of an increase in the fatality rate is linear, while the effect of an increase in transmissibility grows exponentially over time. In the long run, Upsilon will infect more than twice as many people as Epsilon and therefore will result in more deaths, notwithstanding Epsilon’s higher fatality rate.
This is what has made COVID-19 so insidious all along: its low fatality rate bamboozles people into thinking that drastic, life-altering measures of control are unwarranted, even as hospitalizations and deaths skyrocket as a consequence of the uncontrolled transmission.
Question 3 answer is B
The virus will spread more freely in the less-vaccinated community, so Lauren is more likely to be exposed than Jamie. As long as the vaccine is less than 100 percent effective, Lauren is therefore more likely to be infected.
This is why unvaccinated people are, in a statistical sense, a menace to society.