*all serotypes known more than 90 are pathogenic for human
*differentiation of serotypes is important for epidemiology
==antimicrobial resitance==
*first reported in late 1960s
==vaccine==
*PPSV does not induce T-cell dependent immunity
*PCV induces T-cell dependent immunity
*why PPSV still has efficacy in older population while PCV couldn't show higher efficacy than PCV for older population?
*new product "Pneumosil" from India
**10-valent
**serotypes 1, 5, 6A, 6B, 7F, 9V, 14, 19A, 19F, 23F