RECAP with the RBDCOV Community Advisory Panel | Vaccines 101: What are they and how do they work?

Back to the "Blogs" list

ReCAP is a series of interviews with the members of the RBDCOV Community Advisory Panel that will explore the world of community engagement, EU projects and the importance of including people living with immunocompromising conditions in clinical trials. Our first guest is Siegfried Schwarze, retired microbiologist, EATG member and member of the Community Advisory Panel for the RBDCOV project.


Thanks to Siegi for having accepted this interview invitation and for sharing his expertise and knowledge with us. Let’s get started!



Siegi, in your words, what is a vaccine and how does it work?


Imagine your body is like a big castle, and inside this castle there are guards known as the immune system. These guards protect your castle from harmful invaders, like bacteria and viruses.


Now, imagine a vaccine as a training session for these guards. The vaccine introduces a harmless little version of the invader (or sometimes just a lookalike) to the guards without causing any harm or sickness. This helps the guards in recognising and remembering this invader, this foreigner.


So, after this training, if the real invader ever tries to breach the castle in the future, the guards will be well-prepared! They will remember the intruder from their training and will be equipped to defend the castle more quickly and effectively.


In short, with this little story, I wanted to show you that a vaccine trains our body’s defenses to recognise and fight off invaders, keeping us safe!


What are the different types of vaccines available, and how do they differ in their mechanisms of action?


Vaccines can be categorised based on their content and how they are made. Here are some of the primary types of vaccines along with a brief description of how they work:


  1. Live attenuated vaccines: These contain a version of the actual virus or bacteria that has been weakened (attenuated), so it cannot cause a disease in healthy people. Since they are very similar to the natural infection, they are good teachers for the immune system. Examples include: the measles, mumps, and rubella (MMR) vaccine and the chickenpox vaccine.
  2. Inactivated vaccines: These use the virus or bacteria that has been killed or inactivated. The immune system will still recognise it and respond, but since the pathogen (a bacterium, virus, or other micro-organism that can cause disease) is dead, there is no risk of causing the actual disease. Examples include the polio vaccine (IPV) and the hepatitis A vaccine.
  3. Subunit, recombinant, or conjugate vaccines: These contain only specific pieces of the virus or bacteria, not the entire germ. These pieces might be a protein or some sugar from the pathogen. Because these vaccines use only specific pieces of the microorganism, they give a very targeted immune response. Examples include the human papillomavirus (HPV) vaccine and the Haemophilus influenzae type b (Hib) vaccine. And this is also the case of the BIMERVAX vaccine!
  4. Toxoid vaccines: These target the harmful toxins produced by bacteria. The toxins are weakened so they cannot cause illness and are then used to build against the disease-causing parts of the germ, rather than the germ itself. Examples include the diphtheria and tetanus vaccines.
  5. mRNA vaccines: This is a newer type of vaccine. Instead of using the actual pathogen or its components, these vaccines contain a piece of genetic material called mRNA. This mRNA provides instructions to our cells to produce a harmless piece of the target virus (like the spike protein of the coronavirus). Our immune system recognises this protein as foreign and creates antibodies against it. Examples include the Pfizer-BioNTech and Moderna COVID-19 vaccines.
  6. Viral vector vaccines: These employ a different virus (not the one targeted by the vaccine) as a vector. The vector virus is modified to carry some of the genetic material from the virus we want to protect against. When the viral vector is inside our cells, it uses this genetic material to produce a harmless piece of the target virus, which our immune system then recognizes and responds to. An example is the Oxford-AstraZeneca COVID-19 vaccine.


Each type of vaccine offers its own advantages in terms of production, storage, and the type of immune response it elicits. The choice of which type to use often depends on our understanding of how infections happen and how the immune system responds to them.



In your opinion, why do we need vaccines, why are there different types of vaccines available and what’s the point on having new vaccines on the market?


Vaccines are essential tools in public health, and here is why:


  • Prevention of Diseases: Vaccines train our immune system to recognise and face pathogens, like viruses and bacteria. This “training” helps the body to respond swiftly to an actual infection, preventing the onset of the disease or substantially reducing its severity.
  • Herd Immunity: When a significant part of a population becomes immune to a virus or disease, its spread becomes limited. This protection of the collective is known as ‘herd immunity’. It is particularly important for those who cannot get vaccinated due to medical reasons, ensuring they are indirectly protected.
  • Eradication of Diseases: Through global vaccination efforts, some diseases, like smallpox, have been completely eradicated. Others, like polio, are close to eradication.


As for the existence of different types of vaccines and the introduction of new ones:


  • Different Mechanisms for Different Pathogens: Different diseases have different characteristics and attack the body in unique ways. As a result, one type of vaccine might be effective against a particular disease but not another. For instance, live attenuated vaccines might work well for one pathogen, while a subunit vaccine might be the best choice for another.
  • Safety and Efficacy: Some vaccines, especially newer ones, might offer better safety profiles or greater efficacy. Research continuously tries to build upon existing vaccines to enhance their performance or reduce side effects.
  • Varying Populations & Conditions: Some vaccines might be more suitable for specific populations, like the elderly, children or people living with immunocompromising conditions. New formulations might be developed to cater to these specific needs.
  • Pathogen Evolution: Pathogens, particularly viruses, can mutate over time. Sometimes, these mutations can render previous vaccines less effective, prompting the development of new or updated vaccines. A prime example is the influenza virus, which mutates frequently, necessitating annual vaccine updates.
  • Economic & Logistic Considerations: Some newer vaccines might be easier to store, have longer shelf-lives, or be more cost-effective to produce, making them more feasible for broader global distribution, especially in regions with limited infrastructures.
  • Broadening Protection: New vaccines might offer protection against strains or variations of diseases not covered by existing vaccines.
  • Emerging Diseases: As new infectious diseases emerge (e.g., COVID-19), there is an immediate need to develop vaccines to counteract them, expanding the existing repertoire.


In summary, the continuous development and diversification of vaccines are driven by the need to provide optimal protection against an ever-evolving landscape of infectious diseases. They remain one of the most effective tools for preventing diseases, reducing healthcare costs, and saving lives.



Disclaimer: This activity was developed under the RBDCOV Project, which has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101046118.


by Siegfried Schwarze

Get involved

Are you living with HIV/AIDS? Are you part of a community affected by HIV/AIDS and co-infections? Do you work or volunteer in the field? Are you motivated by our cause and interested to support our work?


Stay in the loop and get all the important EATG updates in your inbox with the EATG newsletter. The HIV & co-infections bulletin is your source of handpicked news from the field arriving regularly to your inbox.