These are measuring two different things, aren't they? Your immune system has a 99% chance of preventing you from dying. And this 99% number includes people who were hospitalized, in which case it's not just your immune system that protects you. The vaccine has a 94% chance of you not even getting ill or suffering any long-term effects besides death. As a bunch of people who survived covid-19 report shortness of breath, fatigue and muscle pain 6 months after they contracted it.