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Why Is Ellie Immune In ‘The Last Of Us’? The Game May Have The Clue

Bella Ramsey's Ellie is tough, talkative... and immune.

As most of us eagerly await the next episode of The Last of Us, HBO’s post-apocalytic show taking the internet (and world) by storm, we’re hoping it will bring answers to one of the biggest questions yet to be answered: why is Ellie (Bella Ramsey) immune to the cordyceps infection that has ravaged the rest of the world?

The Last of Us, adapted from the 2013 game of the same name, takes place in 2023, two decades after a pandemic decimated the human population and turned the United States into a wasteland. Rugged survivor Joel (Pedro Pascal) lives in the Quarantine Zone of Boston, until he’s tasked with smuggling 14-year-old Ellie (Bella Ramsey) across former state lines to the rebel group known as the Fireflies.

By the end of episode one, we understand why Ellie is such precious cargo: she’s immune to the cordyceps infection, which turns everyone else into a ‘zombie’ within 48 hours of infection. The Fireflies are hoping to use her blood to develop a vaccine, which until now has elluded mankind.

So far, the show hasn’t come close to answering why Ellie is immune, and the game never came close to giving us a definitive answer. However, the game offers us a few clues the show has so far omitted.

(Minor spoilers for ‘The Last of Us’ episodes one, two and six below.)

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Ellie is the only person in ‘The Last of Us’ universe (so far) who is immune to the Cordyceps infection). (Credit: Getty)

Why is Ellie immune in The Last of Us?

Players of the 2013 game will know that in the winter season, while playing as Ellie, you have the opportunity to look through her backpack and find artefects not yet seen by Joel. One of those is a letter from her dying mother, written on the day Ellie was born.

It hints that the reason Ellie is immune to the cordyceps infection is because her mother was infected while still pregnant. In the final months of pregnacy, the umbilical chord transfers the mother’s antibodies to the fetus, meaning they’re born with some level of immunity. If Ellie’s mum was bitten the day before she gave birth, then the antibodies created by body’s attempt to fight the infection could potentially have been passed on to Ellie.

The letter reads:

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, Anna
Make me proud, Ellie!

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Ellie’s character in ‘The Last of Us’ video game. (Credit: NaughtyDog)

In the real world, newborn immunity fades within a couple months, which is why those early vaccinations are so important. But hey, we’re talking about a fungal infection that turns people into violent zombies here. It’s not exactly based in reality, even if the science behind a Cordyceps infection isn’t exactly fiction.

Ellie’s immunity, explained

In the show, Ellie is almost killed in episode one when a QZ guard tests her for signs of infection. Joel kills the guard, and Ellie shows her bite; it’s clearly old, much older than the one-to-two days it takes to turn. When Joel’s companion Tess (Anna Torv) is bitten in episode two, the differences between the bites is clear. “It’s real,” Tess says of Ellie’s immunity, using her dying wish to ask Joel to transport Ellie safely to the Fireflies, where they’ll hopefully be able to use her blood to create a vaccine.

However, in episode six, a dog that can supposedly ‘sniff out’ infection doesn’t find anything wrong with Ellie. Is it the dog simply not as accurate as man-made technology? Or is the version of the infection she carries different?

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Ellie and Joel in ‘The Last of Us’. (Credit: Photo: HBO)

What weakens the ‘Ellie is immune because her mum was bitten’ theory is the fact that Marlene (a Firefly leader in the Boston QZ, played by Merle Dandridge) doesn’t mention this as a potential explanation as to why Ellie survived her bite, when no one else in history has. Is it why Marlene didn’t have Ellie executed, which is standard protocal for other infected people before they turn? Or was it a lingering loyalty to her mother, Anna?

In the teaser trailer for episode 7, ‘Left Behind’, we go backwards in time to Ellie’s life before she was bitten. After her mother died, she was placed in a military boot camp. One night, she escapes with friend (Euphoria‘s Storm Reid) to explore an abandoned mall, where she comes into contact with the infected.

We don’t yet know how Ellie managed to escape the infected  an immunity to the infection doesn’t make you immune to being torn apart limb from limb  but the episode might provide more insight as to why she’s immune. And if not, we always have season 2 to look forward to.

Stream the entire season of The Last of Us now on Foxtel Now, live and on demand with a 10 day free trial. Start your free trial here.

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