If you are a history buff, you may know that the first vaccine was developed by a man named Edward Jenner, when he found that exposing humans to a cowpox blister – from cows! – protected the exposed human from developing a devastating disease at the time – smallpox! Since that time, vaccines have been medicine’s greatest tool to prevent – and in some cases eradicate – diseases that have historically wiped out entire populations.
Vaccines work by taking advantage of one of our body’s greatest weapons for fighting disease – our own immune system. When our body is exposed to a foreign pathogen or disease, part of its response is to learn – the immune system starts to train itself to be more able to identify and destroy the pathogen. It takes time for the immune system to react and learn, which is not ideal when dealing with a more severe disease – you want the immune system to be primed and ready to fight off that disease, which is where vaccines come in!
When a vaccine is administered, that “dose” is exposing the body to a set amount of inactive pathogen proteins, or proteins chosen because they are close enough that the immune system cannot tell the difference. The immune system will then react locally – which is why soreness for a day or two is not uncommon – bring the pathogen proteins back to a local lymph node, train itself about that disease, then send trained cells and antibodies throughout the body. When those trained cells and antibodies encounter the pathogen later, they can eliminate the threat before it becomes a problem.
Edward Jenner was successful at vaccinating against smallpox with cowpox blisters, because they were similar enough to smallpox that the immune system couldn’t tell the difference – thereby training the immune system to fight smallpox before being exposed to the “real deal.” It was relatively safe to use, because cowpox was not infectious to people. This is how vaccines work – training the body’s immune system to recognize and fight off severe diseases without being exposed to the disease itself.
Vaccines have come a long way since the days of Edward Jenner grinding up cowpox scabs! Modern technology has allowed them to be more refined over the years, reducing adverse reaction risks, improving shelf life with less preservatives, less adjuvants – used to improve the immune response – and they continue to be improved every year.