Is a kid who laughs hysterically every time he is vaccinated (during and after) a future drug addict?

Nope. The few drug addicts that I've come in contact with don't actually enjoy the prick of the needles, its the affect of the drugs they are after. Not being upset by the "pain" of a vaccination in no way correlates with whether or not they'll be addicted to drugs. lol Nice try though.