The advancement of modern medicine helped us to live longer than ever before. Until recently, deaths at or around the age of 30 were very common. The smallpox, for example, was considered one of the deadliest diseases known to humans. Until the smallpox vaccination was found in 1796, the smallpox virus killed 3 out of every 10 people who contracted the disease..
But what are vaccines? And how do they work in the human body?