Most americans born before 1970 have a permanent scar on their shoulders from the smallpox vaccine. why don't younger americans have one?

I believe the answer is: Smallpox has been eradicated by a worldwide vaccination program

Vaccines develop an immunity toward the virus. In order to survive, virus need to obtain a host so they could replicate. Due to the vaccine, the viruses cannot find these hosts. Because of this, smallpox virus started to gradually decreased and eventually eradicated.

the arab empire adopted the muslim religion as their main belief. arabs would influence the people from the territories they invaded towards islam (the muslim belief).

nevertheless, throughout the history of the arab empire, rulers brought intellectual individuals from other religions to their centers of learning. these other foreigners included jews, christians, greeks, persians, and indians.   these resulted in the adoption of important knowledge developed by these cultures by the arabic empire. for example, the works of aristotle were translated from greek to arab and indian scientists brought the numerical concept of "zero" to the arabs.

nowadays, 93% of the arab population is muslim, which at the same time is subdivided in sects including the sunni, zaini, alawi, shia. the remaining 7% is composed mainly of christians.