The official number of people who have survived infection, about 2.77 million, plus the number inoculated, about 5.5 million, equals more than 8.27 million people with some form of immunity, or about 29% of Texas's population. However, there is a hidden variable that is crucial to this calculation: the number of people who have contracted the coronavirus but have not been formally counted - either because they were never tested or were never linked to a positive case. It is impossible to know exactly what this number is, but researchers reckon that it's much greater than what shows up on state data dashboards and the ubiquitous pandemic trackers. A team at Columbia University used a mathematical model to estimate the true scope of infections, and it found that by late January, 31% of Texans probably had contracted the novel coronavirus, which can cause the illness covid-19. This would mean at least 50% of residents may have some sort of immunity - more than the official tallies would suggest, but still well short of Abbott's pronouncement.