Well herd immunity can be achieved with either vaccination or immunity acquired by previous infection.I think both of you are partially right. With some viruses, herd immunity apparently is sufficient without vaccine (a majority don't need a vaccine to manage a seasonal recurring influenza).
With other viruses, you may need.
disclaimer: I speak on behalf of a retired epidemiologist who isn't updated on the late virus market development. That's the step father of my local sausage vendor, Abu Jamil.
Doctor @Dr. Strangelove, @Dark Angel, @vegojimbo, your opinions?