how long immunity lasts depends on the type of the vaccine, the ability of the pathogen to change/mutate ( like the flu virus), and in many cases is only known retrospectively. It could be , to a some degree, assumed that "conjugated" vaccines give you longer immunity. There is no vaccine that is 100% effective....for example, pertussis ( whooping cough) vaccine is only 78-85% effective, but by decreasing the index cases we significantly decrease exposure- what we call "herd immunity". I think the main problem with the current immunization schedule is that it's too cumbersome, and the general public feels it's just "too many" shots.....that's why most doctors are willing to work with patients/families and immunize against the most dangerous diseases first, while "spreading" the not-so-essential shots over time or simply skipping them with mutual understandings of risk/benefit ratio.

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Happy New Year to all! Virtual hugs!