Suppose that a drug company is trying to get approval for a new pain medication that might have some serious negative side effects. How can the company keep regulators from finding any?
Even if you have no training in statistics it is easy to understand that the sure-fire strategy is to focus attention on side effects that are rare. The smaller the number of events, the easier it is to dismiss the few that arise as chance outcomes.
This same strategy for avoiding a discovery is being used now by people who want to keep us from finding that the protection from vaccines diminishes over time.
Data from a study of vaccine effectiveness by the Mayo Clinic shows why severe disease is hard to measure accurately. In such cases, it is better to track a proxy indicator -- a canary in the coal mine -- than the indicator of interest. Vaccine effectiveness against infection is the obvious proxy indicator for effectiveness against all outcomes, which should all vary with the number of infections. Measures of effectiveness of the existing vaccines against infection show unambiguously that the protection provided by the existing vaccines is substantially lower now than it was before the delta variant took over.
A reaction along the lines of “Who cares whether the probability of breakthrough infections is increasing; we only care about preventing severe disease” amounts to saying “Who cares that the canary died; we only care about saving the lives of miners.”
There are two mathematically equivalent ways to describe the protection that a vaccine offers against such specific outcomes as serious disease:
Specialists understand the quirks of these two measures, but the rest of us may not until someone calls attention to them. One of these quirks is that effectiveness activates a cognitive bias that misleads people about the size of any change in the protection offered by a vaccine that is in use.
In the current context, this means that statements about effectiveness will tend to minimize the significance of the fall in protection that triggered the decision to offer a third dose of the vaccines from Pfizer and Moderna.
I have a new post that is available on its own subdomain: https://adtax.paulromer.net
It offers a specific suggestion about a policy that the citizens of the US take change and protect their social and political discourse from the rapidly growing, unchecked power of the two ad-tech giants, Google and Facebook.