Vaccines are not a threat for NNVC.
1. No vaccine is 100% effective. For example, for an influenza vaccine, 60% protection is typical.
2. There are some people who can't benefit from vaccines: those with immune problems, etc.
3. For new emerging diseases, although there are ways to get crude tests of probable effectiveness, you can't do an accurate test of effectiveness until the disease in already in the population and spreading. Because of the way nanoviricides work (host independent) they can be tested before the disease even gets into the human population.
4. Not everyone gets vaccinated for a large number of reasons: fear of the technology, fear of government abuse of vaccine programs (USA), economic limitations, etc.
It will always be necessary to have both vaccines and treatments (which is why I'm heavily invested in both NNVC and NVAX (vaccines) because I consider each to be the best in its field and complementary rather than competitive technologies.