Why Would a Vaccine Help?

“A vaccine works by training the immune system to recognize and combat pathogens, either viruses or bacteria. ... By injecting these antigens into the body, the immune system can safely learn to recognize them as hostile invaders, produce antibodies, and remember them for the future.” Source

But they are saying those that get the novel Coronavirus a second time, their chances of dying go up from the first time they had it. So can someone explain to me why a vaccine for this would be of any benefit? Am I just misunderstanding or does this debunk the efficacy of vaccines (or at least for this virus in particular)?