‘The Last Of Us’ Finale Revealed How Ellie Became Immune To Cordyceps
— Updated on 16 March 2023

‘The Last Of Us’ Finale Revealed How Ellie Became Immune To Cordyceps

— Updated on 16 March 2023
Garry Lu
Garry Lu

A question that has plagued gamers and television viewers alike was answered during HBO’s The Last of Us finale:

How is Ellie immune to the cordyceps infection?

The closing episode of the critically-acclaimed adaptation’s debut season opened with a flashback. Ellie’s mother Anna – portrayed by Ashley Johnson; the actress who originally brought Ellie to life for the original 2013 game – is on the run from an infected while going into labour, and barricades herself in a dilapidated farmhouse.

Armed with nothing but a familiar-looking switchblade as protection, once said infected zeroes in on her location, a struggle ensues. Anna successfully manages to neutralise the rabid assailant, but not before sustaining a fate-sealing bite on her inner thigh.

'The Last Of Us' Finale Revealed How Ellie Became Immune To Cordyceps

RELATED: ‘The Last Of Us’ Season 2 Will Be When S**t Really Hits The Fan

That’s when the camera pans down to reveal that in all the chaos, young Ellie had already been born, with an umbilical cord (ostensibly) pumping the Cordyceps infection directly into her infant system.

Anna frantically cuts the cord and later lies to longtime friend slash Fireflies leader Marlene (Merle Dandridge) that this had been accomplished before the bite, thereby ensuring Ellie would have a chance at living as opposed to facing immediate execution as a precaution.

14 years later, Marlene sheds light on how Ellie (Bella Ramsey) survived the mall attack that claimed the life of Riley (Storm Reid) off-screen and continues to thrive in the face of what is clearly infection.

“Our doctor, he thinks that the cordyceps in Ellie has grown with her since birth. It produces a kind of chemical messenger. It makes normal Cordyceps think that she’s Cordyceps,” Marlene explains to Pedro Pascal’s Joel.

'The Last Of Us' Finale Revealed How Ellie Became Immune To Cordyceps

“It’s why she’s immune. He’s gonna remove it from her, multiply the cells in a lab, produce those chemical messengers, and then we can give it to everyone.”

Of course, once he discovers finding a cure would mean extracting a decent chunk of Ellie’s brain, killing her in the process, Joel violently dispatches the Fireflies – everyone from your nameless guards to the surgeon – eventually ruthlessly gunning down Marlene.

Along with the lie he feeds Ellie, it’s the perfect setup for The Last of Us season (if you know, you know).

Is The Last of Us finale revelation canon?

While the explanation seems pretty clear-cut, apparently there’s still room for speculation.

“It does hint at and give some theories as to why Ellie is immune, even though we don’t answer that conclusively,” HBO show co-creator, video game co-creator, & Naughty Dog President Neil Druckmann stated during a recent press conference (via The Hollywood Reporter).

Druckmann added: “But I think more importantly than that, is it builds the relationship between Marlene and Anna, so that when you get to the end and we put Marlene against Joel, they have their own opposite philosophical terms on how to approach the ends justify the means, knowing how close she was with Anna.”

“And that Anna’s dying wish was, ‘take care of my kid,’ I think gives more weight and maybe more tragedy to Marlene’s sacrifice that she’s trying to make for the betterment of mankind.”

I suppose the hard science was never truly the point.

How is Ellie’s immunity explained in the video game?

As alluded to above, the 2013 video game of the same never truly seeks to explain Ellie’s immunity. Nor does it flashback to her birth with Anna. It does, however, provide players with the following letter:


I’m going to share a secret with you, I’m not a big fan of kids and I hate babies. And yet… I’m staring at you and I’m just awestruck.

You’re not even a day old and holding you is the most incredible thing I’ve done in my life — a life that is about to get cut a little short.

Marlene will look after you. There’s no one in this world I trust more than her. When the time comes she’ll tell you all about me. Don’t give her too much of a hard time. Try not to be as stubborn as me.

I’m not going to lie, this is a pretty messed up world. It won’t be easy. The thing you always have to remember is that, life is worth living! Find your purpose and fight for it. I see so much strength in you. I know you’ll turn out to be the woman you’re meant to be.

Forever… your loving mother,


Make me proud, Ellie!

RELATED: How Much Does Pedro Pascal Earn For HBO’s ‘The Last Of Us’?

Fan theories up until now have usually involved something similar to what unfolded in HBO’s The Last of Us finale (i.e. Anna was infected while pregnant) along with the possibility that Ellie’s father was infected at the time of conception. That being said, to this day, nothing has ever been confirmed.

Later in the game, players stumbled across a surgeon’s recording elaborates on the scientific anomaly:

“Marlene was right. The girl’s infection is like nothing I’ve ever seen. The cause of her immunity is uncertain. As we’ve seen in all past cases, the antigenic titers of the patient’s Cordyceps remain high in both the serum and the cerebrospinal fluid. Blood cultures taken from the patient rapidly grow Cordyceps in fungal-media in the lab… however, white-blood-cell lines, including percentages and absolute-counts, are completely normal.”

“There is no elevation of pro-inflammatory cytokines, and an MRI of the brain shows no evidence of fungal-growth in the limbic regions, which would normally accompany the prodrome of aggression in infected patients. We must find a way to replicate this state under laboratory conditions.”

“We’re about to hit a milestone in human history equal to the discovery of penicillin. After years of wandering in circles, we’re about to come home, make a difference, and bring the human race back into control of its own destiny. All of our sacrifices and the hundreds of men and women who’ve bled for this cause, or worse, will not be in vain.”

'The Last Of Us' Finale Revealed How Ellie Became Immune To Cordyceps - Pedro Pascal Bella Ramsey

Subscribe to B.H. Magazine

Garry Lu
After stretching his legs with companies such as The Motley Fool and the odd marketing agency, Garry joined Boss Hunting in 2019 as a fully-fledged Content Specialist. In 2021, he was promoted to News Editor. Garry proudly retains a blue belt in Brazilian Jiu-Jitsu, black bruises from Muay Thai, as well as a black belt in all things pop culture. Drop him a line at [email protected]


Share the article