The first vaccination occurred at the end of the 18th century, when Edward Jenner exposed a boy to cowpox then later exposed him to smallpox. As he suspected, the boy did not come down with smallpox. Exposure to something causing minor symptoms afforded protection against something that could be devastating. The boy’s immune system had built a response to the cowpox virus and was ready to “jump in” and attack it if it ever encountered it again. The smallpox virus looked so similar to the cowpox virus to his immune system that it could not tell them apart. When the smallpox virus entered the boy’s body, his immune system attacked it before it had a chance to establish and cause disease. Incidentally, the word vaccination comes from the Latin vaccinus, meaning “of the cow”.
If Jenner did that today, he would be prosecuted for reckless medical misadventure, but 220 years ago it opened the floodgates for what is arguably medical science’s greatest achievement. Even more spectacular than the development of soap or anaesthetics or antibiotics, or any of the myriad of other modern technical wizardries.
Vaccines are not treatments but preventers of disease, and they do take a little time to “educate” an individual’s immune system about what bugs to get ready for. As a rule, once an individual is incubating a disease it is too late to vaccinate. Of the scores of animal vaccines available in New Zealand, only the sheep footrot vaccine has curative properties. Response time to different vaccines will vary a bit. Farmers who have not vaccinated their weaner cattle against Blackleg or their lambs against Pulpy Kidney, and are now experiencing losses from these diseases, will find that if they vaccinate now, the sudden deaths will stop a week later.
Two years ago, I was listening to talkback radio and the main topic was vaccination for people. I was aware some people don’t believe the benefits of vaccines are worth the risk of possible side effects, but I was blown away by the breadth and depth of negative attitudes. As a counter, the radio host did cite polio and what a godsend it was when that vaccine came available. Listening to the negative comments, I felt like one of those volunteers who has spent years away fighting disease and starvation in the third world, who then comes home and finds it hard adjusting to others worrying about first-world “problems” with a corresponding lack of appreciation for the good things they have. I was a toddler when the polio vaccine became available, and I was a student when the leptospirosis vaccine for cattle became available. With its introduction the number of dairy farmers catching lepto from the urine of their cows (and being bedridden for a month or two) plummeted.
The use of a vaccine is always like paying insurance. You can gamble that the chances are “it won’t happen to me and mine”, but sometimes it does. Most horses, in my experience are not vaccinated against tetanus. The cases I have seen with this painful disease were all put down before they died of starvation, with muscles so stiff they could not eat. The use of vaccine is also like paying tax. Yes, some of our tax money is wasted, but most of it goes to worthwhile things benefitting others as well as ourselves.
There is a threshold for contagious diseases where if enough individuals in a population are vaccinated and are no longer able to spread that disease, then the causative bug struggles to maintain itself. There has not been an outbreak of distemper in New Zealand dogs for some decades. This is because most dog owners get their dogs vaccinated. Currently, unvaccinated dogs get to live a distemper-free life, not because their owners have paid for vaccination, but because other dog owners have.