Having recently observed World Immunization Week, letâs review the history of vaccination. One thousand years ago, when a wave of smallpox hit India, something extraordinary happened: People lined up to buy the disease. Healers used a cloth to rub a healthy personâs upper arm. Then, theyâd scratch it â just enough to draw blood. The healers would then apply dried smallpox scabs to the area. But hereâs the thing: They would only apply scabs from smallpox patients who had survived the disease. Though people âvaccinatedâ this way would often get sick, most would survive infection and go on to build immunity. (Today, most vaccines in use, including the Pfizer, Moderna and Johnson & Johnson Covid-19 vaccines, are not live vaccines and cannot infect you with the virus they inoculate against.)