"That puts a ceiling on pre-existing immunity at somewhere around 40%."
No, you're assuming that pre-existing immunity excludes people testing positive for the virus. You can test positive while mounting a robust immune response. In fact given that most infections are minimally symptomatic, it's arguable that immunity is the norm, not the exception.
No, you're assuming that pre-existing immunity excludes people testing positive for the virus. You can test positive while mounting a robust immune response. In fact given that most infections are minimally symptomatic, it's arguable that immunity is the norm, not the exception.