• Question: How does injecting weak, dead or viruses that only effect other species stop some life threatening illnesse?

    Asked by acepace33 to Cat, Daz, Johnson on 23 Jun 2011.
    • Photo: Cat O'Connor

      Cat O'Connor answered on 23 Jun 2011:

      Oh Acepace33 what a great question and one that I hope I can answer fully, but i’m sure Daz and Johnson will help me too!

      Vaccination normally works by injecting a person (or animal) with attenuated (so all the bad things taken out) or dead viruses because our body still thinks it’s getting infected with the real deal and will initiate an immune response to try and kill the bug. By tricking our body to do this, it means that if we get infected with this virus for real, the body knows exactly how to get rid of it and will do so really fast, before we even get sick.

      The original smallpox vaccine was based on a virus, very similar to smallpox, that infected mostly cows called….not very imaginative…cowpox! How a cow virus worked to protect people against another human disease is because the two viruses were so similar, especially on their outside skin or coat, that when they infected a person, their body reacted the same way whether they were being attacked by smallpox or cowpox! This meant that if you could infect or vaccinate a person with the mild cowpox disease, then their body would know exactly what to do if they got infected with smallpox so that they wouldn’t get sick! And this is exactly how it works for other diseases too!

      Am I making sense? This was the first sort of immunology (study of how our immune system works) I learned and boy was I confused for ages!!

      Hope I’ve answered your question!


    • Photo: Darren Braddick

      Darren Braddick answered on 23 Jun 2011:

      Hi acepace33

      Sure Cat, I can assist and take over ;). OK, well consider a single disease – smallpox is the best example and the one Cat used. Smallpox is slightly related to cowpox, another virus. Smallpox is extremely dangerous and was a truly horrific disease.

      The immune system has two parts – one is called innate, and is basically the reaction – think of it like the body of a human. The other is called adaptive, and is more like the brain of a human. The innate is not specific, and will attack anything with some power. Because it is not specific, if you get the same disease twice, the immune system will respond the same each time – think of colds, which you get loads of through the year. Each time, the same disease happens!

      But in smallpox and cowpox, the body can learn – using the adaptive immune system, and recognise the disease the second time. So the first time, you get ill (and some people will die :() but maybe you survive, and your body learns. That means, if you get ill again, your body will be much quicker and much stronger to kill the disease.

      Because cowpox is a lot like smallpox, and because smallpox is so deadly, the idea of vaccination in this case came because you can trick the adaptive immune system of humans to think it has experienced a disease once, by giving it ‘fake’ virus.

      All of this happens because the adaptive system recognises shape on a very small level. The viruses are made of proteins and those proteins have specific shapes which the adaptive immune system can ‘learn’. Luckily, the mild cowpox virus seems to look enough like the smallpox one that you trick the immune system to be protected against both disease if you vaccinate with the mild one!

      Of course, the same trick can be used with many viruses and diseases – and usually done by injecting dead or damaged viruses particles which cannot infect you, in the hope that they stimulate your adaptive immune system to ‘remember’ the shapes on the surface of these particles.

      I hope this helps answer your question!

      Please vote and let us know if we can help anymore!