How do vaccines work?

Lesson 6

What is the science behind vaccines?

Learning outcomes

  • Students will understand how vaccines use the bodies immune system to protect against pathogens
  • Students will understand that there are different types of vaccinations
  • Students will understand that not everyone can have a vaccine and that herd immunity protects vulnerable individuals
  • Students will use scientific knowledge and critical thinking and perspective taking skills to evaluate different opinions about vaccination

 

Pathogen: A bacterium, virus, or other microorganism that can cause disease

Herd immunity: A form of immunity that occurs when a significant part of the population is vaccinated and can provide protection for individuals without sufficient immunity

Science understanding

Biological sciences

Describing how the requirements for life (for example oxygen, nutrients, water and removal of waste) are provided through the coordinated function of body systems such as the respiratory, circulatory, digestive, nervous and excretory systems

Explaining how body systems work together to maintain a functioning body using models, flow diagrams or simulations

Investigating the response of the body to changes as a result of the presence of micro-organisms

Science as a human endeavour

Scientific understanding, including models and theories, is contestable and is refined over time through a process of review by the scientific community

Advances in scientific understanding often rely on technological advances and are often linked to scientific discoveries

People use scientific knowledge to evaluate whether they accept claims, explanations or predictions, and advances in science can affect people’s lives, including generating new career opportunities

Values and needs of contemporary society can influence the focus of scientific research

Science enquiry skills

Formulate questions or hypotheses that can be investigated scientifically

Analyse patterns and trends in data, including describing relationships between variables and identifying inconsistencies

What is a vaccine?

A vaccine contains an altered (attenuated) version of a pathogen, its toxin or a protein/particle from its outer coat

The altered state of the pathogen could be weakened or dead. Sometimes only a part of the pathogen is used in a vaccine  – called the antigen

There are new cutting edge vaccines that only use DNA and mRNA from the pathogen

 

How do vaccines work?

A vaccine causes the body to produce antibodies and memory cells that act against the target pathogen, without making the person ill 

If a vaccinated person is later infected by the same pathogen, their immune system recognises it and can destroy it very quickly

Vaccines build herd immunity 

Herd Immunity

Herd immunity (also called herd effect, community immunity, population immunity, or social immunity) is a form of indirect protection from infectious disease that occurs when a large percentage of a population has become immune to an infection, whether through vaccination or previous infections, thereby providing a measure of protection for individuals who are not immune

In a population in which a large proportion of individuals possess immunity, such people being unlikely to contribute to disease transmission, chains of infection are more likely to be disrupted, which either stops or slows the spread of disease

The greater the proportion of immune individuals in a community, the smaller the probability that non-immune individuals will come into contact with an infectious individual, helping to shield non-immune individuals from infection

Meet Prof Robert Booy: 10 and 20 years ago, discussing herd immunity

Prof Booy has researched the benefits of vaccination for 35 years

Class activity

Scenario 1 – No vaccination

All the students stand up in the room. They must be within arms reach of each other

Choose one person to have a disease, such as tuberculosis, which is spread through coughing

They are given a card of red dot stickers which represent TB. (They should also have a red dot sticker on to show that they have the disease)

When they “cough” they pass the card on to the person standing next to them – they have now caught TB and will keep a red dot sticker

This person then “coughs” and passes the card along

Eventually the whole class will have been passed the card have a red dot sticker on and have therefore “have” TB

Scenario 2 – 50% vaccinated

Set the scene as for scenario 1 but this time randomly give 50% of the class green stickers – this means half the children will not be protected

Now, have the sick person “cough” again but now they can’t pass the red stickers to anyone with a green sticker – they are protected from the immunisation

Half of the class will be protected. See how far the red sticker can get 

It will likely still make some children sick, but not all.  This not a full herd immunity but a partial immunity

Scenario 3 – 90% vaccinated

Set the scene as for scenario 1 but this time randomly give 90% of the class green stickers – this means only 2 or 3 children will not be protected

Now, have the sick person “cough” again but now they can’t pass the red stickers to anyone with a green sticker – they are protected from the immunisation

Most of the class will be protected

Because the red sticker can’t be passed further than one person at a time, the “unvaccinated” students should be safe

This is called herd immunity and is vital to protect vulnerable members of our society

World Health Organisation – How Do Vaccines Work?

The Children’s Hospital of Philadelphia – Vaccine Science: Evaluating Scientific Information and Studies

High School | The Vaccine Makers Project

Coming soon

Coming soon

Summary

A vaccine protects against an infectious disease. It contains an altered (attenuated) germ or an outer bit of the germ which stimulates the body to build antibodies to protect against the infection

Herd immunity is built when enough people have had a vaccine and have had the infection and survived

Quiz

1) Vaccines
a) Are chemicals that teaches the body’s immune system how to fight diseases
b) Is a really cool English indie rock band
c) Are altered versions of pathogens or their toxins that teaches the body’s immune system how to fight diseases
d) Are altered versions of pathogens or their toxins that cause infections

 

2) _______ is when a large enough percentage of the population is immune to a disease to stop it spreading, thereby protecting those who are not immune
a) Community immunity
b) Herd immunity
c) Population immunity
d) All of the above

 

3) A vaccine works by
a) Killing the pathogen in the body
b) Teaching the body to produce antibodies and memory cells to act against the pathogen without making the person ill
c) Producing antibodies and memory cells to act against the pathogen without making the person ill
d) Changes the pathogen’s DNA so it doesn’t work anymore

 

4) A bacterium, virus or other microorganism that can cause disease is a
a) Pathogen
b) Parasite
c) Illness
d) Symbiote