The COVID-19 pandemic has exposed people across the globe to large amounts of statistical data. Previous studies have shown that individuals’ mathematical understanding of health-related information affects their attitudes and behaviours. Here, we investigate the relation between a) basic numeracy, b) COVID-19 health numeracy and c) COVID-19 health-related attitudes and behaviours. To do this, an online survey measuring these three variables will be distributed in Canada, the United States, and the United Kingdom. Health numeracy is expected to mediate the relation between basic numeracy and COVID-19 related attitudes and behaviours. Multigroup analysis will also be used to investigate mean differences between the countries as well as differences in mediation coefficients. Further, the moderating effect of political leaning and COVID-19 related anxiety will be examined.