Former studio employee Gabriel Betancourt spoke about The Last of Us. He recalled an idea that, according to him, Neil Druckmann had discussed.
Betancourt said that a concept was considered in which "several people have immunity" and even "an entire group of such people." This significantly changes the series' usual rule, where Ellie's uniqueness was a key element of the story.
He also conveyed Druckmann's words: "I want to tell a more complex story," featuring "many characters" and an expansion of this theme. Such an approach could have led to new conflicts and a larger-scale narrative.
At the same time, this is only one of the ideas. Over the years of development, the concept could have changed.