[Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] [Tag] We can test the thresholds to see what particular threshold must be met to have high confidence in protection. No value is perfect and, like you state, titers are indirect measures of protection. But for many pathogens, there is extremely strong correlation to enable inference.