This again…?
Let’s not exclude this little nugget that can be found in that same article:
“British Troops Were Protected by Herd Immunity
Washington also knew that his American-born soldiers were far more susceptible to the disease than the European enemy. That’s because smallpox was endemic in England, meaning that a high percentage of British troops had already contracted the disease as children and now carried lifelong immunity.”
In other words.. if you were already infected with COVID you have this little thing called “Herd Immunity”. Therefore, we carry the lifelong immunity.