Page 5 of the data from Walgreens gives an explanation: "All results, including the positivity rates by vaccination status graph, are unadjusted. The team has

Page 5 of the data from Walgreens gives an explanation: "All results, including the positivity rates by vaccination status graph, are unadjusted. The team has observed that the positivity rates among unvaccinated individuals seen on the bar graph appear to be lower in comparison to vaccinated individuals. Furthermore, repeat testing among those who were previously positive in the last 90 days appear to confound the results. The team conducted additional analyses examining characteristics of the patient population by vaccination status and the impact of excluding recent COVID-19 cases (5.0% of total tests). Findings show that the unvaccinated group are typically younger and healthier, less symptomatic and less likely to report direct COVID-19 exposure or recent travel compared to vaccinated groups. Controlling for recent COVID-19 cases, results show that the unvaccinated group has a 17.1% higher positivity rate compared to the 3-dose group. Controlling for additional factors leads to a larger difference between groups." So basically, if you take out the negative repeat tests that were associated with a previous positive test, the phenomenon that this entire Substack post is based on disappears.