In Lesson 1 we covered the history behind vaccine development. The good news is that you care enough to come back and read Lesson 2, but the bad news is that there is a high likelihood that you didn’t share Lesson 1, and that is a problem. For the sake of the general public, share Lesson 1 and then share this post too! We can only hope to get trolled as hard as we did yesterday!
Let us begin our lesson!
So, yesterday we left off at the turn of the 21st century with the introduction of a number of vaccines and the eradication of several major diseases. The big question is how on earth did they do it?! What tools did they use to actually develop these vaccines, and what were they injecting into people to stop the spread? Let’s answer those questions today!
Let’s start back in time with the first true vaccine, the cowpox virus that prevented smallpox. That was a “live” or active virus that caused an infection which prevented another more serious infection. This method is not used anymore, for hopefully obvious reasons, but this is how our immune system works naturally. We get infected, our body fights it off, builds an immunity and then prevents reinfection (which will be the topic of tomorrow’s lecture).
The most closely associated version of this natural immune response is using a virus that is “dead” or inactivated. The pathogen is “killed” by any number of methods, such as radiation, antibiotics (in the case of bacterial vaccination), or heat, to name a few. These methods either destroy the pathogen or render it non-functional so it cannot cause an infection, but can still be recognized by the immune system. Vaccines of this type include influenza, bubonic plague, polio, and rabies.
Killing a virus or bacteria is easy, but keeping it alive but unable to cause an infection is not. Despite the difficulty, this is done very frequently in the form of “live, attenuated” vaccines. These contain the full pathogen which is modified in such a way that makes it unable to elicit a full infection in the individual. They do have risks in individuals with compromised immune systems, but are overall very safe. The Measles, Mumps, and Rubella vaccine (MMR) is an example of this type, along with yellow fever and typhoid.
With the advent of recombinant DNA technology in the early 1970’s, and the other advances in the field of biochemistry and molecular biology that came around that time, it then became possible to move into a second generation of vaccines that didn’t use the entire organism at all: recombinant protein and peptide vaccines. These vaccines were composed of smaller fragments of the pathogen’s proteins that were responsible for the immune response in the host. Injecting just these pieces allowed for a complete immune response without the risk associated with using the entire pathogen, and was widely developed for HPV, Hepatitis B, and the plague.
Further advances in biotechnology lead to the ability for gene synthesis and highly efficient plasmid (small, circular strands of DNA mainly seen in bacteria) production and purification. This process ushered in a new era of vaccine technology, the DNA vaccine. The concept of the DNA vaccine is that it stimulates the immune system by essentially making a recombinant protein or peptide vaccine within the host’s own cells, which triggers an immune response that is a blend between first and second generation vaccines. There are a number of benefits to using DNA, including the stability in transit and the ease of administration without needles.
Vaccine technology continues to be a massive area of growth for the biotechnology and pharmaceutical industry. There are a large number of diseases which are thought to be suitable targets for vaccines, but takes lengthy research and development processes as well as 4 phases of clinical trials in humans before a new vaccine is even considered for the market. The cost of doing this is often a barrier for drug companies, but may also keep vaccines out of the hands of the world’s poorest people. (I will cover this more in another lesson.)
Well, that is pretty much all you need to know about the major types of vaccines. With any luck you now have the necessary information to start some intelligent conversations (or intelligent arguments, either one). So go forth and pick fights with the anti-vaccers, and make your teacher proud! (Seriously though, call someone out this month. It is #ImmunizationMonth after all.)
