It all started with an observation. Edward Jenner, an English physician, observed that milkmaids who contracted cowpox were rarely victims of smallpox epidemic, a disease that in?icted a heavy toll on humankind with an estimate of 500 million victimsworldwide.In1796,Jennerinoculatedtheextractedfluidfromblistersonthe handofamilkmaidwhowasinfectedwithcowpoxintothearman8yearoldpeasant boy. After the boy recovered from a mild illness caused by this inoculation, Jenner exposed him to smallpox and to his delight the boy did not develop the disease. He published his work in 1798 in three publications titled “Vaccination Against smallpox”, where the term vaccination is derived from the Latin word “vacca” meaning cow. Jenner was recognized to be the father of modern immunology, and hisworkmarkedthecommencementofanewdawninmedicinethatledtothe1979 declaration by the World Health Organization (WHO) of the global eradication of smallpox. By the beginning of the 20th century, vaccines for typhoid fever, rabies, polio, plaque and diphtherias were in use, and nowadays we are equipped with effectivevaccinesagainstmorethan20infectiousdiseasessuchasmeningitis,rubella, whooping cough, rabies, and hepatitis B among others.