> the pigs appear entirely immune to more than 99% of the known versions of the PRRS virus, although there is one rare subtype that may break through the protection.

If there's already a variant of the virus that can overcome the edit, then without additional measures it will simply go from 1% of the case to 100% and the disease is going to be as prevalent as before and the benefit of the tech will be null after just a few years.

(Except that it will draw negative light on CRISPR-based gene editing , slowing down actual progress. That's the curse of GMO: companies making them for bad reasons and reducing collective trust in what is a very promising and important technology for long term food security)