Interesting. Note that people with B-cell deficiencies (CVID in particular, but SIgA and I think others–these deficiencies are often not diagnosed until adulthood) are well known to have chronic OPV infections (more than 5 years in several cases), which evolve over time. The viruses are considered vaccine-derived polioviruses if they’re more than 1% from the original Sabin virus, and are designated iVDPV. iVDPVs can often (usually, I think) be distinguished from circulating VDPVs (cVDPVs) by a high level of non-synonymous mutations in particular parts of the capsid. cVDPVs, by contrast, arise in populations with low vaccination coverage, where the virus (usually Sabin 2) is transmitted serially, presumably with little immune pressure. cVDPVs have a much higher percentage of synonymous mutations (as you’d expect). IVIG treatment of chronically infected people with CVID may also play a role. There have been instances, in countries where polio has been eliminated, of iVDPVs have been detected and identified in wastewater. In at least a couple of those cases, I believe they attempted (unsuccessfully) to trace the individual by following up the sewage lines and testing at the branches.
Note also that a chronically infected person also would be a setup for recombination.