Introduction to Vaccination

00:01 If you’re wondering, what has immunology ever done for me? Well the answer’s quite simple -vaccination; a really easy procedure that protects all of us from infectious disease.

00:14 Vaccination is providing protection by utilizing either pre-existing components of the immune response or more commonly, by inducing the generation of antigen-specific memory cells.

00:28 We can divide immunization into active or passive immunization.

00:34 The most common form is active immunization where there is injection of antigen.

00:40 This often requires additional components, for example an adjuvant.

00:46 The immune response is generated in vivo.

00:50 It takes time to develop but it provides long term protection because there is generation of memory T-cells and memory B-cells in response to the vaccination.

01:02 There is the potential to develop both a cell-mediated and a humoral response.

01:09 In contrast, passive immunization is the injection of pre-formed antibodies.

01:16 This provides immediate protection, but the protection is short term.

01:22 Antibody has a half life of about three weeks in the circulation.

01:26 So the protection provided by these injected antibodies doesn’t last for a very long time.

01:34 It only provides humoral immunity.

01:37 The pathogen needs to be susceptible to antibody mediated destruction.

01:42 If cytotoxic T-cells are required, then passive immunization will not be helpful.

01:48 And there is the risk of adventitious pathogen transfer.

01:52 Let’s have a look at some examples of passive immunization.

01:57 Horse antisera against snake venom, botulism toxin and diphtheria toxin can be administered to individuals exposed to these toxic agents.

02:11 Pooled human immunoglobulin against Hepatitis A or B, measles, rabies, tetanus, varicella zoster, and humanized monoclonal antibody against respiratory syncytial virus can all be given to patients that are exposed to these agents.

02:36 With regard to active immunization, vaccines can induce neutralizing antibodies.

02:45 Viruses need to bind to cell surface receptors on cells in order to infect cells.

02:51 Antibodies can block the binding of viruses to their cell surface receptors.

02:58 Bacteria can produce toxins, these can poison our cells.

03:04 Antibodies can block the toxic activity of bacterial toxins.

03:11 Finally, in order to establish an infection, many microorganisms need to colonize surfaces in the body.

03:19 Antibodies, particularly dimeric secretory IgA can prevent colonization.

03:27 Let’s have a look at the immunological basis of active vaccination.

03:32 Here we have a diagram showing you the magnitude of the immune response following the first encounter with antigens from a pathogen.

03:41 This will be a natural infection that we would be exposed to.

03:45 The primary immune response is fairly weak and short lived.

03:52 However, if instead of encountering the natural infection, that is potentially pathogenic, we give a modified version of the pathogen; in other words the antigens are seen in a non-pathogenic form.

04:08 Then we elicit this primary immune response.

04:11 And importantly, memory T-cells and B-cells are generated.

04:18 Looking at the secondary immune response, if the subsequent encounter is with the actual pathogen itself, the individual goes straight into making a secondary immune response because the primary immune response was elicited by the non-pathogenic form.

04:38 And now there is a secondary immune response which is strong and long lasting.

04:45 And this occurs in response to the actual pathogen upon the first encounter.

04:52 So because memory cells are already present as a result of the vaccination, a secondary immune response occurs on the first encounter with the pathogen.

05:02 This is here really just for your information.

05:05 I’m not going to read through this.

05:06 You can read through it at your leisure.

05:09 But it provides you with the current vaccination schedule for the USA.