Vaccines have been hot news again recently. The world waits on bated breath to see the results of the COVID-19 vaccine roll-out and a promising end to quarantines and lockdowns. But it has raised many questions. Among these are “what are vaccines?” and “how do vaccines work?” Join us as we break it down and explain the ins and outs of vaccination.

What are vaccines?

Let’s keep it simple. A vaccine is a biological preparation—usually given using an injection or nasal spray—to help the body prevent against infection.

Vaccines help the body fight against pathogens, disease-causing organisms, that are all around us. They give a level of immunity against the disease allowing the body to fight it and stay healthy.

How do we get infections?

Pathogens cause infections. When they enter the body, they can cause a variety of problems. Today, we know that there are four main categories of pathogens. These include:


Composed of DNA or RNA (aka genetic code and coated with protein, viruses work by invading the body’s healthy cells, making copies of themselves, and then invading more cells in the body. This creates an infection.

Types of virus include:

  • Common cold
  • Flu
  • Measles
  • Herpes
  • HIV and AIDS
  • Norovirus and Rotavirus
  • Meningitis
  • COVID-19


Bacteria is all around us. Some of it is good for us, such as Lactobacillus, some not so much. Bad bacteria is known as pathogenetic bacteria, and this causes bacterial infections in the body. Luckily for us, bacterial infections can often be treated by antibiotics or the body’s natural immune response.

Types of pathogenetic bacteria include:

  • Tuberculosis
  • Urinary tract infections (UTI)
  • E. coli
  • Gonorrhea
  • Cellulitis
  • Salmonella


No, these are not just the mushrooms you might be eating for dinner. Fungi is so much more. The world is filled with millions of types, and they can grow in various environments. Fungi have a nucleus, covered by a membrane, which is then protected by a thick cell wall. This can make them very difficult to get rid of. Inside the body, fungal infections can take root and cause all sorts of issues. But luckily, we have some ways of fighting back too.

Types of fungal infection include:

  • Thrush
  • Ringworm
  • Athlete’s foot


These are live body invaders that can cause all sorts of problems. Usually, they thrive by feeding off a living host and spread through contaminated food, water, and soil, or even blood.

Types of parasite diseases include:

  • Toxoplasmosis
  • Malaria
  • Lice
  • Worms
Note: Vaccines don’t work against all types of pathogens! That’s why it’s vital, if you’re feeling unwell, to consult your healthcare provider.

How do vaccines work?

Vaccines work by helping the body develop a proper immune response to an infection. This is done by imitating an infection (but more on that later). This causes the body’s natural immune system to create the antibodies to protect itself against the virus. These can later be reproduced using memory cells, if and when the body encounters the actual disease and protect the body against infection.

Without a vaccine, it can take days for the body’s natural resources to create the appropriate antibodies to fight a disease. Sometimes this takes too long, and it can leave the body weak, result in serious symptoms or even death.

What types of vaccines are there?

Not all vaccines are created the same way. Various methods are used to make sure the vaccine gets the job done. Let’s take a look at the different types out there today.


Using heat, chemicals, radiation, or other agents, inactivated vaccines contain virulent matter that is inactivated. This means it is able to provoke an immune response but will not cause the disease.

Examples of inactivated vaccines:

  • Polio vaccine
  • Hepatitis A vaccine
  • Cholera vaccine
  • Pertussis vaccine
  • CoronaVac (Sinovac COVID-19) vaccine


These types of vaccines are what’s known as a live vaccine. But that doesn’t mean you’re just being injected with a virus and left to fend for yourself. No! Instead, the virus is weakened, so it does not cause the disease (in healthy people) but does create a sufficient immune response.

Examples of attenuated vaccines:

  • MMR (measles, mumps, and rubella)
  • Varicella (chickenpox)

Viral vector

Viral vectors are one of the most modern technologies being used to make vaccines. They work by using a modified version of a virus, or piece of the virus, that is harmless to create an immune response. For example, by the spike protein found on the surface of the COVID-19 virus, viral vectors are able to help the body recognize the disease and fight against it.

Types of viral vector vaccines:

  • Oxford—AstraZeneca vaccine (COVID-19)
  • Sputnik V (COVID-19)
  • Zabdeno/Mvabea Ebola vaccine


Using chemicals or heat, toxoid vaccines contain an inactivated toxin that has been rendered harmless. This allows the body to develop a response and protect itself against the disease.

Types of toxoid vaccines include:

  • Tetanus
  • Diphtheria
  • Botulinum

Subunit, recombinant, polysaccharide, and conjugate

This vaccine group works by using a specific part of the pathogen, and using it to provoke an immune response. As the disease is “dead” and small particles are used, these types of vaccines are sometimes considered less risky than others. However, the recipient may need a booster shot.

Types of subunit, recombinant, polysaccharide, and conjugate vaccines include:

  • Hepatitis B
  • HPV (Human papilomavirus)
  • Whooping cough
  • Pneumococcal disease
  • Shingles


RNA or mRNA vaccines are specifically designed to teach our bodies how to respond to a disease and fight it. These types of vaccines are contemporary and have the potential to target diseases such as Zika, rabies, and cytomegalovirus. Contrary to misinformation online, mRNA vaccines do not alter DNA as it does not enter the nucleus of the cell where DNA is stored.

Types of mRNA vaccines:

  • Pfizer-BioNTech (COVID-19)
  • Moderna (COVID-19)
All the vaccine types mentioned above are approved for use following tried and tested technology. While some are newer in their usage as vaccines, that does not mean they are unsafe or untested.

Vaccine FAQ

Below we’ll quickly answer some of the most commonly asked questions about vaccines to help you get the answers you need.

Can I still get sick if I’ve had a vaccine?

100% effectiveness is rare for any vaccine or medicine. However, to receive licensing, vaccines do have to be proven to work. That said, it is possible to still to get sick. When deciding whether or not to have a vaccine, here are some points to remember:

With a vaccine, you might get sick, but are at a much lower risk of serious complications or death.

There may be a gap between the time you take the vaccine, the time it takes to work, and exposure to an illness

In the case of the flu, you may have a different strain or another respiratory disease.

I’m healthy. Can’t I just let my body fight off a virus by itself?

It might. However, you would be putting yourself at significant risk of serious complications or even death. For example, diseases such as meningitis or measles can have life-lasting consequences. Vaccination allows you to develop your immune system to fight infection in a controlled environment, which lowers the risk for you.

Are vaccine side effects a good sign?

Site pain, fatigue, flu-like symptoms, if you’ve experienced these after a vaccine, you might be thinking, “YES! My vaccine is working!” And it’s true. It is working. But your symptoms or side effects, won’t tell you how effective it is.

Whether you develop side effects or not after a vaccine is no indicator of how effective it was. Providing it was administered correctly, you should be protected. So side effects or no side effects, your vaccine is working.

Do vaccines cause autism?

NO! This myth originates from a “study” headed by Dr. Andrew Wakefield. It involved only 12 children and was quickly revoked by the author itself on the grounds of providing insufficient data and undisclosed financial interests. As a result, Dr. Wakefield’s medical license was revoked. In the wake of this study, several others were conducted to establish whether there was a link between autism and the MMR vaccine—all of them came up blank.

Does herd immunity work?

Yes! Herd immunity works. But probably not like you think it does. Herd immunity protects those who, for one reason or another, are unable to be vaccinated. This may be because of low immunity or allergies, etc. Due to a high uptake in the vaccine, the virus is unable to spread, and thus, the vulnerable person is protected. This is herd immunity.

Now, say no one took the vaccine or very few people. The virus is able to spread easily, and the vulnerable person is more likely to be infected.

What is a vaccine passport?

A vaccine passport is a document or record that shows you have received certain vaccinations ahead of travel. Although it has faced criticism as being discriminatory, for example, against those who cannot be vaccinated, it is conceived to make travel easier. Showing a vaccine passport (or record of vaccination) can help travelers avoid quarantines and other additional tests.

Whether or not it will be used in practice is currently a hot topic of debate, with the EU’s “Green Digital Certificate” and the US’s version under discussion in a battle of civil liberties vs. health and safety.

Are vaccine passports legal?

Vaccine passports fall into a legal grey area, and there is no straightforward legal answer, to date, as to whether they are 100% legal or not. While no one can force a person to vaccinate, the restriction of access to particular services may be legal in terms of protecting the right to life (Article 3 HRC). At the same time, everyone has the right to autonomy and to make decisions regarding their health. Forced vaccination would be in violation of the right of liberty. That’s why currently, many countries are facing the challenge of whether or not to introduce a “vaccine passport” or equivalent in relation to COVID-19.

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Written by Maria Isabella Neverovich
Maria is an Irish writer, Health Editor at Verv, lover of forests, mountains and all things nature. She enjoys discovering new vegetarian dishes, creating...
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