https://clinicaltrials.gov/ct2/show/NCT04327206
https://clinicaltrials.gov/ct2/show/NCT04328441
It seems there are no current clinical trials for OPV, just that author arguing that such trial could be started (first time in April).
BTW, looking at how polio manifested, it really is a good example about what viruses are able to do, and why only counting "dead" (as in CFR or whatever) misses the point:
https://www.cbc.ca/news/canada/manitoba/covid-19-is-threaten...
"Polio often destroyed nerve cells that controlled muscles, leaving some with paralyzed limbs or lungs."
Sometimes these are chunks of toxins that your body recognizes a toxic, but without the actual part of the toxin that causes the toxicity. A kind of flag but without the army behind it.