THE SYNTHETIC BIOLOGY PROJECT
ALL ABOUT VACCINES
Answering your vaccine questions!
Vaccines protect us from infection and illness, keeping our community safe from diseases. Vaccines save millions of lives every year globally, and overall has saved more lives than any other medical invention in history.
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Let's take a closer look below!
Your immune system
Your immune system is a complex network of vessels, organs and immune cells that work to protect you from infections and diseases [1]. Viruses, bacteria, parasites, fungi or other infectious agents that can make you ill are called pathogens.
When you get sick, your immune system uses all these defences to protect you. One of the key components of the immune response are immune cells called B cells and T cells. B cells help fight the infection by producing antibodies, which are small proteins that target and neutralise the infectious pathogen. T cells help kill infected cells, to prevent the pathogen from spreading.
Your immune system also has special memory cells, called B or T memory cells, that store a “memory” of the pathogen, by remembering particular proteins found on the pathogen. These proteins are called antigens, and are specific to each strain of pathogen. So, if you come into contact with the pathogen again, your immune system can immediately recognise it and respond faster and better next time. However, this whole process takes a lot of time.
Vaccines are important as they can help train our immune system without making us ill.
Parts of the immune system
Hover over the labels for more!

lymphatic system: a filter system for the fluids in your body, which immune cells travel in to detect potential foreign infectious agents.
thymus: immune system organ that make different sorts of immune cells and proteins. the thymus makes white blood cells called T-cells!
stomach acid: the highly acidic content of your stomach helps destroy many pathogens
bone marrow: immune system tissue that make different sorts of immune cells and proteins. white blood cells called B-cells are made in the bone marrow!
saliva and tears: enzymes in your saliva and tears help break down pathogens!
respiratory tract: the mucosal lining in your lungs help protect against foreign pathogens
skin: forms a physical barrier against foreign infectious diseases
spleen: immune system organ that helps filter your blood and make immune cells and proteins to fight infections.
digestive tract: the mucosal lining in your digestive tract help protect against foreign pathogens

antibodies: made by B cells, that are an essential part of the immune system and vaccine response. They mark pathogens so that immune cells can find and fight them.
pathogens: infectious microbes such as viruses, bacteria, parasites, fungi that can make you sick!
white blood cells: aka immune cells, work together to fight infection in your body. This includes B cells, T cells, natural killer cells, macrophages, and many other immune cell types.
How vaccines work
If you were naturally infected by an infectious virus or bacterium (aka a pathogen), chances are that you would become very sick. However, by using vaccines, we can build up our immune defences without getting sick.
Vaccines contain a version of the pathogen that is harmless to you, but still helps your immune system recognise the pathogen so it can start preparing to give you immunity against the real pathogen [2,3].

There are different types of vaccines: usually made of either a weakened or inactivated version of a virus or bacterium, or a harmless component of them. mRNA vaccines are an exciting newer development where temporary genetic instructions are used as a vaccine, allowing the antigens to be made by our own cells (see more on these in our previous snippet!)
Essentially, these weakened or partial forms of the pathogens contain protein structures called antigens on them. Your immune cells then store a “memory” of these antigens, via the antibodies and B and T memory cells mentioned before. So then, if you encounter the real virus/bacterium, your immune system recognises it straight away and can defend your body against it quickly, preventing you from becoming sick.
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Vaccines are not only important for yourself, but also to protect the people around you. This is due to something called herd immunity.
What is herd immunity?
Herd immunity helps keep our community safe, particularly vulnerable people who aren't able to get vaccinated (usually due to age-related reasons or compromised immune systems). If enough people are vaccinated, then this slows down the spread of disease from person to person.
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Herd immunity only works if enough people are vaccinated. The percentage of vaccinated individuals needed to achieve herd immunity differs per disease, for example measles needs 95%, whereas polio requires 80% [2].
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Vaccines have had a long history, from the 15th century when people attempted to protect themselves from smallpox by exposing themselves to small, mild doses of smallpox. Australia introduced major vaccination programs in the 1960s and 1970s, saving thousands of lives each year. Vaccine research continues today, protecting us from many infectious diseases like whooping cough, chicken pox, measles, and COVID-19 [3].
References:
1. Department of Health & Human Services. Immune system [Internet]. Department of Health & Human Services; 2022 [cited 2023 Sept 2]. Available from: https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/immune-system
2. How do vaccines work? [Internet]. World Health Organization; 2020 [cited 2023 Sept 2]. Available from: https://www.who.int/news-room/feature-stories/detail/how-do-vaccines-work
3. Department of Health & Human Services [Internet]. 2022 [cited 2023 Sept 2]. Available from: https://www.betterhealth.vic.gov.au/health/healthyliving/vaccines/
4. Australian Government Department of Health and Aged Care. National Immunisation Program schedule [Internet]. Australian Government Department of Health and Aged Care; 2023 [cited 2023 Sept 2]. Available from: https://www.health.gov.au/resources/publications/national-immunisation-program-schedule?language=en
5. How flu viruses can change: “drift” and “shift” [Internet]. Centers for Disease Control and Prevention; 2022 [cited 2023 Sept 2]. Available from: https://www.cdc.gov/flu/about/viruses/change.htm
6. Remmel A. Covid vaccines and safety: What the research says [Internet]. Nature Publishing Group; 2021 [cited 2023 Sept 2]. Available from: https://www.nature.com/articles/d41586-021-00290-x
7. Williams SN. Vaccine hesitancy is one of the greatest threats to Global Health – and the pandemic has made it worse [Internet]. 2023 [cited 2023 Sept 2]. Available from: https://theconversation.com/vaccine-hesitancy-is-one-of-the-greatest-threats-to-global-health-and-the-pandemic-has-made-it-worse-208227
8. Goldenberg MJ. Vaccine hesitancy: Public trust, expertise, and the war on science. Pittsburgh: University of Pittsburgh Press; 2021.
