Part 1 The truth about vaccines – I want COVID-19 to go away too, but you’re going to be injecting me with what?!


COVID-19 has certainly left its mark on 2020, and the race is on to create a vaccine that will see borders reopen, economies flourish, and most importantly, allow us all to be healthy and return to our normal, non-social-distancing lives.

In this three-part series, we aim to debunk some of the myths and allay some of the concerns that have sprung up regarding vaccines in general, and the COVID-19 vaccine in particular. In this first part, we take a closer look at what vaccines are made of and how they work.

What is a vaccine?

Vaccines provide protection against the effects of pathogens (disease-causing organisms). Each vaccine works against a particular pathogen so that, once you have been vaccinated against it, you will experience milder symptoms and a shorter duration of illness, if you happen to become infected by the pathogen in question. Basically, your immune system remembers encountering this pathogen previously (in the form of the vaccine) and springs into action, preventing you from experiencing the full force of the infection.

Various forms of vaccines are available and are specially designed to help your body fight particular pathogens.

The components of a vaccine

The ‘active ingredients’ in vaccines are called antigens. These are particles related to the target pathogen. They are supported by adjuvant ingredients that help your immune system recognise the antigen. Other components include preservatives or stabilisation agents and fillers or diluents. 

Contrary to the urban legends that abound about vaccines, they do not contain microchips, tracking devices or substances that specifically and directly cause conditions such as autism or Alzheimer’s disease.


Antigens are small particles derived from the pathogen that the vaccine is designed to work against. These viral and bacterial particles may be used in different forms and vaccines are classified accordingly. 

  • Live (attenuated) vaccines contain live but weakened versions of the pathogen.
  • Inactivated vaccines contain killed versions of the pathogen.
  • Subunit, recombinant, polysaccharide and conjugate vaccines contain certain parts of the pathogen.
  • Toxoid vaccines contain a toxin produced by the target pathogen.

Live (attenuated) vaccines

These contain a weakened (attenuated) form of the pathogen and mimic a natural infection. This means the vaccine provokes a strong immune response, leading to lifelong immunity after just one or two doses. Unfortunately, such vaccines must be kept cool, making them difficult to administer in regions without ready access to refrigeration. They may also be unsuitable for people with weakened immune systems. Live (attenuated) vaccines are typically used to immunise against:

  • Measles, mumps, rubella (MMR)
  • Chickenpox
  • Rotavirus
  • Yellow fever
  • Smallpox.

Inactivated vaccines

These contain a killed version of the pathogen. Inactivated vaccines must be administered in multiple doses, as they typically don’t invoke a strong enough immune response to create lifelong immunity. Inactivated vaccines are typically used to immunise against:

  • Hepatitis A
  • Rabies
  • Flu
  • Polio

Subunit, recombinant, polysaccharide and conjugate vaccines 

These vaccines incorporate pieces of the pathogen which may include sugars, proteins or the casing (capsid) of the pathogen. These types of vaccines can be administered to a wide cross-section of the community as they create a very targeted immune response. However, they often require repeated doses (boosters) to invoke prolonged immunity to the pathogen. Subunit, recombinant, polysaccharide and conjugate vaccines have been used to immunise against:

  • Shingles
  • Hib (Haemophilus influenzae type b)
  • HPV (Human papillomavirus)
  • Hepatitis B
  • Pneumococcal disease
  • Meningococcal disease
  • Whooping cough (as part of the DTaP vaccine).

Toxoid vaccines

These vaccines contain toxins produced by the pathogen to create immunity. As the immune response is targeted to the toxin, immunity is invoked for the disease-causing part of the pathogen, rather than the pathogen as a whole. In these vaccines, the toxin has been made safe, however is still antigenic, and is typically adsorbed to aluminium or calcium salts which act as the adjuvant. Toxoid vaccines have been created to protect against:

  •  Diphtheria
  • Tetanus.

New types of vaccines that are being developed include DNA vaccines that produce strong long-term immunity, and recombinant vector vaccines that act similarly to a natural infection and are effective for invoking immunity to the pathogen.

Thimerosal, mercury, alum and more. 

These are the adjuvants, preservatives, stabilisers and diluents that make up the ‘scary’ ingredients you see listed on some vaccine information sheets. You’re probably wondering why they’re in there. Let’s take a closer look at what they do.

Some parents are concerned about harming their children by administering vaccines containing scary-sounding ingredients listed on information sheets.


Alum or aluminium acts as an adjuvant and is commonly found in tiny amounts in vaccines. Often, it’s specifically present as aluminium hydroxide, aluminium sulphate, and/or potassium aluminium sulphate.

Adjuvants are required because the pathogenic particles or toxins in vaccines (antigens) have been weakened, killed, or broken into tiny pieces to isolate specific proteins or sugars. Without the adjuvants, your immune system probably wouldn’t notice the antigens and, if it did, it would take care of the problem fairly quickly. As a result, you may not achieve immunity to the pathogen. 

The adjuvant works like a neon sign for your immune system, alerting it to the presence of a foreign substance and signalling that your immune system needs to get off its (metaphorical) butt and do something about the stuff that’s just entered your body.

And what about these alum or aluminium ingredients causing Alzheimer’s? There have been many conflicting reports on the effects of aluminium on the progression of Alzheimer’s disease, and researchers have not been able to conclusively demonstrate that aluminium directly contributes to Alzheimer’s disease. When you consider that approximately 5% of the daily intake for this bio-metal occurs through drinking water, the amount received via vaccines pales in comparison.

Preservatives and stabilisers

Thimerosal (a mercury-based preservative) is used in certain vaccines. It is common knowledge that ingesting mercury is hazardous to health, so you may wonder why scientists would put it in a vaccine?

The answer is simple. Preservatives and stabilisers play vital roles in keeping the vaccine safe and stable. Stability and freedom from contamination are important properties of vaccines since they must last long enough to get from the manufacturer to your doctor or community nurse and then to their patients. In areas without access to refrigeration, the vaccine’s ability to remain stable at room temperature is especially important in order for the vaccine to remain effective. 

Thimerosal specifically works to prevent contamination of the vaccine container by fungi or bacteria. What’s more, the amount of mercury contained in a typical dose of vaccine is minimal. In fact, you’ll probably ingest just as much mercury in a serve of canned tuna. Also, it is metabolised differently to naturally occurring mercury. 

Another important property of vaccines is ease of handling. The vaccine needs to be easily extracted from the container it arrives in so it can be administered to the patient. Oils or sugars are typically added as stabilisers to give the vaccine a longer shelf life and to ensure it doesn’t stick to the sides of the container so that you’re getting all the antigens and adjuvants required from a single dose.

Other ingredients

Vaccines also contain diluents or fillers such as sterile water or saline solution. These ensure that the tiny amounts of antigens and adjuvants required for immunity are delivered in a volume that is large enough to be easily handled and effectively administered by health workers.

You may have heard that vaccines containing egg protein or formaldehyde. These are residual components, left over by vaccine manufacturing processes. They are usually only present in miniscule amounts, if at all. 

How are vaccines administered?

Vaccines are typically administered orally (i.e. swallowed) or intravenously (through an injection needle). Although the immune system may react immediately, it typically takes 10–14 days to achieve immunity. Any redness around the injection site, fatigue or slight fever after receiving the vaccine is a sign it’s working correctly.

Help from the herd: Herd immunity occurs when enough people have received a vaccine or have been exposed to a particular pathogen.

What is herd immunity?

Herd immunity is achieved when enough people in your community have received a vaccine or been exposed to the pathogen. The exact percentage of exposure required to achieve herd immunity is largely dependent on the targeted pathogen. In Australia, we aim for 95% of the population to receive all specified vaccines in order to achieve herd immunity against a wide range of diseases. 

Once herd immunity is achieved, there is little risk of widespread transmission of the pathogen(s), and those who have been vaccinated will experience milder symptoms and a shorter disease duration, if they become ill at all. This means that those who are vulnerable—babies, young children, the elderly, people with medical conditions or those who are immunocompromised or unable to receive some vaccines due to their medical condition—remain protected.

Find out more about vaccines in parts 2 and 3 of this series

In the second part of this series, we will take a closer look at how vaccines are designed and developed, and in part 3 we will look specifically at the challenges of designing a COVID-19 vaccine. 

Got questions?

If you have any questions or would like advice on safely handling these and other hazardous substances, please contact the Chemwatch team today. Our friendly and experienced staff draws on years of experience to offer the latest industry advice on how to stay safe and comply with Health and Safety regulations.


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