1.19 patchnotes state that immunity gained from high hydration and energy levels was decreased "on average." I assume the primary reason for this was to stop players from being completely immune to diseases like salmonella while having maxed hydration and energy. After doing some testing I believe it is now impossible or virtually impossible to cure colds with high stats alone which I assume is unintentional but in any case is a bad change because colds are very easily to get; a player can get them simply by spawning with blue temperature so it made a lot of sense for colds to be relatively easy to cure once the player was able to get healthy stats.