What lies did Joel tell in The End of America?

They were going to take Ali to a guardian and send him back to the army, but when they got to the church, they found everyone dead. On the way, they found that Ali was immune to spore virus, and then Joel took Ali to find fireflies to make antibodies to save mankind. People come to be born again. After a year of ups and downs, Joel and Ellie formed an inseparable relationship. Finally, they bought more westernmost goods, crossed the whole United States, and finally reached the finish line. Joel excitedly took Ellie to the hospital. They fell into the water because of an accident, and both of them fell into a coma. Joel woke up and saw the firefly queen in Boston in the first chapter. When he woke up, he asked where Ellie was. They said that in the operating room, according to the tapes and materials, Joel knew that Ellie would die if the antibody rose. Because they are like the feelings between father and daughter, Joel doesn't want Ellie to die. Even if human died, he didn't want to see the tragedy happen again, so he killed the firefly queen, rescued Ellie and fled back to Uncle Tommy's dam. On the way, Ellie woke up in the car and asked, Why did we leave? Joel lied and told him: people with such immune function don't know you, others have already been here, and we already have the antidote! Finally, back to the dam. . . . In the last video conversation, Ellie mentioned that he was not alone when he was bitten. His friends were there. They were bitten together, but Ellie didn't die. He watched his friend mutate and be killed by himself (see DLC: Lost in America) to comfort Joel and asked Joel if all the fireflies he said were true. Joel said it was because he didn't want Ellie to think about his body and make it. This is the case.