Reasons Behind Ellie’s Immunity to the Virus — The Last of Us 

One of the core aspects of The Last of Us series is Ellie’s immunity. Her immunity against the Cordyceps virus is the sole reason for Joel to escort her across the country in the first game. Ellie was bitten by a runner, weeks before the narrative of the first game begins. 

A normal person is said to turn within two days of getting bitten, as stated by Joel, but nothing of sort seemed to happen to Ellie.  

The reason for Ellie’s immunity is not clearly stated in any of The Last of Us games, but there are theories and evidences supporting it which could possibly answer the age-old question about her immunity.  

1. Reasons behind Ellie’s immunity to the virus  

I. The cordyceps virus in Ellie is dormant 

It is theorized popularly that Ellie is still infected but the cordyceps inside her is in a dormant state. In the Left Behind DLC, both Ellie and Riley get bit by a runner but in the end, only one of them survives the transformation. Riley, unfortunately, does not survive.  

It could be possible that the runner that bit Ellie was unique, meaning it had a different strain of the mutation which was dormant but that would be just lazy writing. It is worth remembering that Ellie got bit three weeks before the narrative of the first game starts so more than enough time had passed for her to turn into an infected.  

II. Ellie’s mother, Anna 

Another popular theory connects Ellie’s immunity to her mother, Anna. The theory states that Anna got bit shortly before she gave birth to Ellie. The infection caused Ellie to be exposed to the cordyceps virus as a fetus which made her completely immune to the virus.  

During the winter season, while playing as Ellie, you can look through her backpack which contains artifacts, notes and letters which Joel did not pick up. Among these artifacts are things like Riley’s Firefly pendant or the robot toy that Ellie gave to Sam. But that’s not all! One of these artifacts is a letter from Ellie’s mother, Anna.  

Contents of the letter: 

“Ellie,  

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!” 

Anna

III. Ellie is not exactly “immune” 

Yes, that sounds impossible but there are a lot of theories suggesting that there is more to her “immunity” than meets the eye. Theories suggest that Ellie isn’t actually immune, the cordyceps inside her are acting extremely slow, leading her to eventually spiral into insanity.  

In the games, it is pretty well established that the infected people quickly lose their minds before turning into a runner. The transformation is extremely quick but theories state that Ellie’s case is different. The virus inside her brain is causing her to get more rageful in the second game as she constantly makes the terrible decision of continuing her quest for revenge.  

Remember, Ellie says the following in TLOU 1: Back in Boston – Back when I was bitten, I wasn’t alone. My best friend was there. And she got bit too. We didn’t know what to do. So…She says, ” Let’s just wait it out. Y’know, we can be all poetic and just lose our minds together.” I’m still waiting for my turn…  

What if she is slowly turning into a runner just like every person infected by a runner eventually becomes, and all her thoughts, decisions and actions are driven by her slowly creeping insanity from the fungus mutation inside her brain? Guess we will have to wait for Part 3 to get an official answer!  

2. Did the Fireflies find any other immune survivors?  

Even though Joel lies to Ellie, stating that the fireflies have found other immune survivors, that is not the case. In the games, it is made clear that Ellie is the only one immune to the virus and she’s the only hope mankind had at creating a vaccine to cure the infected.  

The Fireflies, unfortunately, did not succeed at finding any other immune survivors except Ellie. Due to this reason along with the death of Jerry Anderson, the only doctor who could potentially create a vaccine, the Fireflies disbanded.  

3. Who else knows about Ellie’s immunity?  

The only people to know about Ellie’s immunity, other than Joel, are Tommy and possibly Maria. Joel speaks to Tommy about Ellie’s immunity as soon as they reunite. Him knowing about the immunity possibly confirms that Maria knows about it too.  

In The Last of Us Part 2, Dina gets to know about Ellie’s immunity to the virus during a cutscene where Ellie breaks her gas mask and is able to breathe spores without getting infected. Dina, horrified, tries to share her gas mask with her thinking Ellie would get infected, but she stops her saying that she is immune to the virus.  

Abby Anderson also obtains this knowledge about her immunity as her father, Jerry Anderson, is the doctor who was tasked with creating the vaccine. Being her daughter, Abby gets to know about Ellie’s immunity while Jerry was determining ways to create the vaccine.  

4. Why does Ellie wear a gas mask in The Last of Us Part 2?  

Many might think this is a major plot hole in the second game but it’s not. Ellie, even though she’s immune, wears a gas mask to hide her immunity from Dina and the other residents of Jackson. Even if she told anyone, no one would believe her therefore she keeps it a secret.  

Additionally, Ellie has a tattoo of a moth covering up her bite mark. According to Neil Druckmann, the tattoo on her forearm has different layers of meaning to it. Moths are symbolic of death, but for Ellie, the moth represents her compulsion to seek revenge for Joel’s murder. The moth also symbolizes Ellie and Joel’s relationship which also explains the moth on Ellie’s guitar – a gift from Joel.  

5. About The Last of Us Part II

The Last of Us Part II is a an action-adventure game developed by Naughty Dog and published by Sony Interactive Entertainment for the PlayStation 4. The game is set 5 years after the events of the first game.

Players control Ellie on her journey for revenge against The Wolves, a faction which has set up in Seattle. On her journey, Ellie fights against survivors of the Cordyceps apocalypse and new variants of the infected. The game mixes elements of stealth and gun-play in vast areas, allowing players to approach the situation as they see fit. The Last of Us Part 2 received an overall positive reception and has gone on to win several Game of the Year awards.