Module 4: Vaccination and Epidemics

These free OCR A Level Biology Vaccination and Epidemics revision notes have been written for specification point 4.1.1(l).

Vaccination

Vaccination stimulates the production of memory cells without causing illness. 

It exposes the immune system to a harmless* antigen, stimulating the production of complementary antibodies and memory cells.

*Although it should be noted that side effects (such as allergic reactions) are possible, and in rare cases, the vaccine does not work. 

Forms of antigenic material in (some) vaccines:

• Antigens: A selection of antigens from the pathogen, such as hepatitis B.
• Attenuated microorganisms: A weakened and harmless pathogen, such as the measles and TB vaccines.
• Dead microorganisms: Killed so that they are harmless, such as cholera.

Vaccination Programmes

Vaccination protects individuals from pathogens, but the immunisation of large groups of people can strategically protect nonimmune and immunocompromised people.

Two key elements are:

• Herd Immunity: When enough of the population is immune, the pathogen’s spread is highly reduced.
• Ring Vaccination: All individuals who have or may be in contact with someone who is infected are vaccinated to prevent the pathogen from spreading.

Controlling epidemics

The occurrence of disease is monitored at both a national and an international level in both animals and humans to prepare for and prevent the possibility of an epidemic or a pandemic.

Outbreaks in animals are monitored due to their economic importance in the food supply (e.g. cattle), as well as their ability to spread diseases across borders (e.g. wild birds).

The table below outlines some of the key considerations when managing epidemics with vaccines: