Vaccination

Yup, another post where I'll have to cross my fingers and pray that I won't start a flame war... I've already discussed a lot of this content in an earlier post, but I will be going into more detail.

Define vaccination and immunisation

While these two terms are generally used interchangeably, they actually have subtly different meanings. "Vaccination" just means that you received a vaccine, whereas "immunisation" means that you actually developed immunity. Vaccination does not always result in immunisation, as a certain percentage of people will not develop immunity from a given vaccine.

Describe the different types of vaccines- eg. live attenuated, killed cellular vaccines and acellular vaccines, and their particular advantages and disadvantages

See earlier post: Vaccines and Immunotherapy

• Live attenuated- Attenuation is achieved by either targeted recombinant DNA techology, or by random mutations induced by a change in growth conditions (e.g. culturing an organism in animal cells, rather than human cells). The first attenuated vaccine was the BCG vaccine (which is for TB, but offers some protection against leprosy). It was created by 13 years of in vitro culture of M. tuberculosis. (Dedication!) Other examples include some polio vaccines, MMR, yellow fever, chickenpox and hepatitis A (there are also killed version of hep A and polio vaccines).
• Killed cellular vaccines- Contains an intact but non-living organism. Examples include some polio and hep A vaccines, rabies, influenza, pertussis, typhoid, cholera and Q fever vaccines. The cholera vaccine only offers protection for around 6 months, which is why it's pretty much only recommended as a travel vaccine.
• Toxin-based vaccines- Contains an inactivated but immunogenic toxin (i.e. a toxoid). Exmaples include tetanus, diphtheria, some cholera vaccines, and a C. perfringens vaccine for lambs.
• Subunit vaccines- Subunits either purified from microorganisms or produced with recombinant DNA technology. Often needs to be combined with an adjuvant, which I will describe in the next section...

Understand what adjuvants are (with examples)

As mentioned here, subunit vaccines often require an adjuvant in order to stimulate an immune response. Aluminium hydroxide is one of the most common adjuvants- it works to concentrate an antigen at an appropriate site. Another common adjuvant is tetanus toxoid. There are, however, many other adjuvants that are being trialled. Liposomes and immune-stimulating complexes (ISCOMS) help to deliver antigens to antigen-presenting cells, bacteria (such as B. pertussis) can stimulate cytokines, and cytokines themselves might be useful in activating an immune response, particularly in immunocompromised patients.

Be able to describe modern vaccine developments

As I just mentioned, many new adjuvants are being trialled. There are also many vaccines under development for other diseases, such as malaria and HIV.