Types of Vaccine

The variety of bacteria and organism in the world around us is truly staggering, and because of the diversity in size, shape, form, and function of different pathogens, there are in fact a number of different kinds of vaccination, all designed to prepare you for infection at the hands of the most virulent and contagious diseases out there.

The different types of vaccines

There are actually a number of different kinds of vaccination in current use, and these are:

• Live attenuated vaccines: Composed of weakened versions of the viruses and bacteria responsible for disease, this type of vaccine is extremely effective and can provide strong, lasting immunity against the illness in question after as little as a single dose.
• Inactivated vaccines: Are made up of pathogens that have been rendered harmless through anyone of a number of different methods including radiation, heat, and chemical treatment. Once injected into the body, these pathogens take no action themselves simply because they can’t, however they still possess their own identifying characteristics which drives the immune system to work against them.
• Subunit vaccines: These are not composed of whole pathogens, and are in fact made up of preparations of viral and bacterial ‘subunits’, parts of these organisms which the body recognises and targets for an immune response. The specific regions responsible for an immune response are called epitopes, and these are sometimes the subunits found in this type of vaccine.
• Toxoid vaccines: These vaccines don’t contain any component of the actual disease causing pathogen. Instead they carry inactivated versions of toxic chemicals that some bacteria release to cause disease. These are only used where the toxin in question is what causes the disease, and by supplying the body with a harmless version of the toxin (called a ‘toxoid’) it learns to defend itself against it.
• Conjugate vaccines: Some bacteria are distinctive in that they have a protective coating of molecules called polysaccharides. This coating is a defensive mechanism which also works as an effective disguise, concealing bacteria from immune systems (particularly young and immature ones). These coatings can be targeted through conjugate vaccines, which are preparations of recognisable molecules and toxins which stick to polysaccharide coats and make the bacteria in question extremely recognisable.
• DNA Vaccines: Can be made specific to viruses and bacteria whose genetic code has been analysed in detail. These vaccines have yet to enter public use, but they are being tested in small human groups and are achieving some significant successes. These vaccines don’t make use of the original pathogens or any part of them, instead they involve synthetic strands of DNA identical to the pathogen in question. Once this has been introduced into the blood stream, some cells take this DNA up and prepare to work against the pathogen.
• Recombinant Vector Vaccines: These are also experimental vaccines being developed. In these a bacterium or virus is used to deliver pathogen DNA rather than just injecting the DNA into the blood stream (as in DNA vaccines).

Why do we need different types of vaccines?

Diversity in the types of vaccination we have at our disposal is important when it comes to successfully immunising people against a variety of different pathogens. Each of these microbes will have their own unique biology and modes of action, and while many can be arranged into groups that are roughly similar in terms of morphology and how they work there is still a great deal of variety to contend with. This is one of the issues our immune system must deal with to provide us with effective protection, a huge variety of different pathogens all looking to infect us.

A range of vaccination technologies means that we are able to develop vaccines particularly suited to certain kinds of pathogen. This limits risks and ensures that we are powerfully immunised against a range of diseases.

Constantly developing new vaccination technologies means that we get closer to vaccines for particularly dangerous conditions for which we currently have no protection. A vaccine for dangerous conditions like meningitis B and HIV are, for example, being pursued to save countless people across the world from suffering from these life threatening conditions. 

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