<p>I think there's a possibility of Joel being immune, but it's slim. It's more of a Shrodinger's Cat situation. Until LOU2 is released, we'll never know, but until then we can view Joel as both Immune and not Immune.
</p><p>However. The listening ability is merely a game mechanic, and the death scenes for Joel and Ellie in the game are non-canon Game Overs, as many people say. It's the same as how you can recharge the flashlight just by shaking it (Which by the way is impossible. It may work a few times, because as the battery becomes low smaller flashlights will think it's out of juice so shaking it CAN make it work again, but only until the battery is completely drained.)
</p><p>Sarah couldn't have been confirmed nor denied as Immune, as she was killed via a firearm (And unlike The Walking Dead, they don't turn even after dying by normal means) If a host body died before turning, even if shot in the heart, the virus won't be able to take over as the body is dead.
</p><p>And actually, the Cordyceps Virus IS real, though at the moment it's only strong enough to take over insects. But it does have the same effects on insects IRL as it does humans in the game. Doing some research on Cordyceps can prove this point. And, as it is a real virus, and the game isn't as far-fetched as most games in the genre, it can be said that the Cordyceps Virus of The Last of Us has the same rules as real life viruses. Example, the spores die if they enter an environment with fresh air. Even mushroom and mold spores need a damp environment to spread, which is why Black Mold is common in homes with water leakage, and you only see spore clouds in buildings with tight spaces that are near water (The most spores we see in any location are in the building with the humans where you face all those stalkers, clickers, and that bloater). So any spores on Joel would become benign when he leaves the damp space and enters an environment with fresh air. Of course, it's only a game mechanic when he ONLY wears the mask in the spore clouds.
</p><p>Back to Joel's 'immunity'. Immunity can be genetic in certain cases. Immunity happens from genetics adapting over time. an example of this is ants. about 50 years ago, any pesticides we used would kill them, But since the ants breed and give birth thousands of times faster than humans do, they quickly evolved to become immune to those pesticides, so now we have to use specific chemicals on them. So it's possible that Ellie is not the only one immune to the Virus. However there could be a deeper theory on HER immunity than just thinking about Joel's immunity. Perhaps Ellie was even experimented on as a child. She was born only 2 years after the Virus started killing the mass population of Earth. And the Fireflies, who have had a MAJOR part in her life could have done something to her, since Marlene didn't seem so shocked about Ellie's immunity and was so willing to take her life to cure the virus.
</p><p>However, if the immunity was randomly occuring, to the point that people who were well into their adult lives when the virus struck, it would be a small dormant genetic that causes the immunity, and would be completely random, and Sarah might have had it as genetics are hereditary, but we'll never know.
</p><p>Also along the line of random occurances of immunity. If you think about it scientifically. Humans as a species don't become immune to things they haven't been exposed to on some level. We didn't evolve to be immune to small pox until the past generations took the vaccine as children and adults, and it took years for us to be immune to Measles/the Black Plague. So basically, Joel wouldn't be able to be immune in this case, since he'd be too old when the virus strikes to develop an immunity. Immunities mostly develope when we're young which is why we're constantly legally required to get vaccinated before attending school when we're children. Which is probably why Ellie is immune. Experimentation or not, Ellie was born INTO the world filled with the Cordyceps Virus. Perhaps her mother inhaled spores shortly before giving birth. Not enough to infect, but JUST enough to be broken down and inhaled into Ellie while she was still in the womb, idk. It's possible.
</p><p>This post wasn't to confirm nor deny your theory, but to explain things you should think about when making such a theory.
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