HPV - doesn’t work that way, sadly. It’s not like MMR or DPT, where once you get above a certain percentage, you start seeing the effects of herd immunity.
Actually, herd immunity applies here, too. Herd immunity means that the chain of infection is broken, so that even if a person is exposed to the disease, they cannot transmit it to another person. This graphic illustrates the principle. The means of disease transmission does not affect the process; the pertinent factor is that the disease is passed from person to person. Herd immunity does not work, for example, with tetanus.
That’s because Tetanus isn’t a communicable disease. Neither is HPV. The difference between the two is that there are substantial variances in disease vectors that are dependent on human behaviour. This is why even if you inoculated 80 percent of people, the disease would still be endemic.