What implication does long-term viral residency have for herd immunity thresholds?
The effective pool of susceptible individuals may fluctuate differently than with purely transient infections
The persistence of the virus, or its genetic fragments, within a significant portion of the population long after recovery alters how traditional herd immunity models function. In typical acute infections, once an individual clears the pathogen, they are removed from the susceptible pool until re-exposure occurs, leading to a clear, transient decrease in susceptibility. However, if individuals harbor the virus long-term, the dynamic calculation of the effective pool of people vulnerable to new infections becomes more complex. This fluctuating susceptibility pool differs significantly from scenarios where viral clearance is swift, meaning that achieving a certain level of population immunity might not translate into the same level of transmission reduction as expected with pathogens that are cleared rapidly from the host system.
