The Sense of Vaccines

Vaccination works. There's no real reason to doubt that. How many people do you know who suffered from small pox, polio or even measles? I don't think I know anyone who had any of these diseases. All thanks to vaccines. Still, it appears, there are many 'skeptics' on the internet who doubt the efficiency of vaccination. Mostly, I suppose, because they're afraid to harm their children by vaccinating them. Odd, since there is absolutely no evidence whatsoever that vaccination is harmful for children and tons of evidence that it is beneficial. Most of those 'discussions' end in shouting wars and I've had a look at some of the blogs about the topic, but I really can't be bothered reading them (this one hurts my eyes!). They're generally very badly written by people who don't seem to have a clue what they're talking about.

Fortunately for you, there's me. I'm a natural skeptic and I never stop asking questions, but if the data overwhelmingly show that vaccines work and there is no evidence (none!) to the contrary, what is there to be skeptic about? In this present post, I'll provide you with some evidence that vaccines really work (but seriously, why do you even doubt that?) but I'll also explain why and how they work. I know that true believers can not be convinced with evidence and I would normally leave them alone. However, in this case, the believers (that is the 'vaccines are evil' crowd) are actually endangering all the rest of us. Many infectious diseases besides small pox would have been extinct already if the viruses that caused these diseases hadn't found a safe harbor in the bible-belt.

As I mentioned, I don't really understand the anti-vaccine lobby. Their websites are horrible and the arguments against vaccines, as far as I've seen them, are mostly false. Let me start with a little graph that shows the efficacy of some common vaccines.

From Immuno Biology, 5th Edition, by Janeway et al.

Diphtheria, Polio and Measles have all virtually disappeared from the USA since the vaccination campaigns started against these diseases. Small pox and rinderpest have been eradicated world wide. These diseases have been around for a very long time. For over 10,000 years (!) people have suffered from small pox. Now it's gone. Completely gone. Is this just a coincidence or a consequence of the world-wide vaccination campaign?

Let me explain how vaccines work and why they work, if I haven't convinced you yet that they work. There are five basic types of vaccine: killed, attenuated, toxoid, subunit and conjugate. Plus there are some experimental vaccines still under development, that may be safer and more effective than existing vaccination strategies.

Killed vaccine is rather obvious: it's the virus or bacterium that causes the disease but killed so it can not multiply and cause disease anymore. Injection of the whole thing will fool your body into thinking it's infected and prepare the immune system for an actual infection. Killed vaccines are generally safe, but can make you a bit sick. This has to do with your innate immune system over-reacting to the contents of the vaccine and isn't really anything to worry about.

Attenuated vaccines are live vaccines. Those can be dangerous. It is essentially a mutant of the same virus as the one causing the disease. The attenuated mutant is not infectious anymore and should not make you sick (at least no more than the killed virus), however, there's a very small chance that the attenuated virus has mutated back to a wild type, active, virus. This is why large-scale vaccination against, for example, measles, can sometimes lead to a small, localized, outbreak of the disease. Attenuated vaccines are not ideal, but they generally generate a better immune response that the other vaccine variants.

For toxoid, subunit and conjugate vaccines, only a small portion of the pathogen, the virus or bacteria that causes the disease, is used. A small dose of toxin, for example tetanus toxin to protect against tetanus infection, can also make you a bit sick, but not as sick as the real deal and it certainly won't kill you. I can't really find any reliable numbers on vaccine-induced deaths, most of the claims are on the anti-vaccine sites that hurt my eyes and the sources are unclear. Attenuated vaccines can result in a lethal disease, true. But the odds are very small and they are obviously being avoided now. It's a bit of a trade off, really, what would you rather have? A small illness from the vaccine? Or death form the disease? If the disease does not occur in your region, there's obviously no reason to get vaccinated and risk vaccine-related illness. I never got vaccinated for yellow fever, since I've never traveled to South-America where this disease occurs. I would get vaccinated if I were to travel to South-America, since I'd rather risk illness from the vaccine than death from yellow fever. Plus, if I don't get vaccinated, there's a chance I'll bring the disease back with me and infect others! This brings me to the bible-belters.

In the bible-belt, and there's one in every country, people believe that diseases are punishments from their god and should be accepted. If god wants to kill their children, well, then he must surely be lonely in his heaven! This, at least, is an argument a certain pope used when the children of Rome were dying of small pox (or some other disease, I can't remember). The problem is, however, that is they don't get vaccinated, diseases like mumps and measles can hide out in their compounds and will every now and then rear their ugly heads. As a consequence, children outside the bible belt will have still have to be vaccinated. If that vaccine makes them sick; the actual disease is worse. If only everyone would just accept the vaccine, those diseases could be exterminated and with them, the need for population-wide vaccination!

Now, why is it, then, that we have to keep vaccinating against certain other diseases, such as the flue? The problem with some pathogens is that they don't just infect humans, but also certain animals. The flue virus hides in birds and pigs as well. If we want to get rid of flue, we would have to vaccinate not just all the humans, but also all the birds and pigs in the world. That's a bit much, isn't it? Especially since flue keeps re-combining, changing it's coat, inside those pigs and birds!

Below, I've posted a graph to demonstrate again that vaccination works.

From Immuno Biology, 5th Edition, by Janeway et al.

What this graph shows is that when you challenge an animal (a rabbit in this case, but it could be a mouse or a human too, same thing, really) with an antigen (in other words: when you vaccinate it!) you get a certain response after a lag phase of a few days. Now, if you challenge the animal again with the same antigen (in other words: when the animal encounters the actual pathogen after vaccination) the response is much faster and much higher. While the response to another antigen (B), that the animal did not encounter before, is much lower and slower. This proves that vaccination works and that is specific. The immune system has remembered antigen A and can now mount a faster, better response to it when it sees it again. I will explain how that works in the next update, since I feel that this one is quite long already and I'm afraid you might get bored if you have to read too much...