Martin Kulldorff and Jay Bhattacharya:

Throughout the pandemic, the media have eagerly compared Covid statistics between different countries. But such comparisons are often deceptive.

Take, for example, the use of Covid case counts. These depend not only on the number of people infected but also on the amount of testing performed. While useful for evaluating whether cases are increasing or decreasing within a particular country, they are deceptive when comparing countries. If we truly wanted to know, it would be easy, through random seroprevalence surveys that measure the proportion of people with antibodies. But not all governments have been eager to conduct these surveys, while some scientists have even got into trouble for doing them.