Herd Immunity (HI)
Where majority is vaccinated, transferal rate reduces
If proportion vaccinated fell, HI is lost (70s whooping cough)
Vacc. rate fell 80-30%; Ks of children infected, many died
Global vacc. program - tetanus (mothers, newborns), polio, measles
WHO - 95% of children, 2 doses measles vacc. (global HI)
85% get first, 56% get second; takes money, determination
Individual & global economy adv.