Health experts, scientific researchers, and professional medical groups often advise people to seek immunization. In fact, immunization itself is achieved primarily by taking vaccines. Getting immunized is critical for at least two motives:
- To guard yourself against infections
- To defend the ones round you
Therefore, vaccines are the best way we ought to prevent infectious diseases, and there’s several vaccine types. Every type teaches your immune system how to fight germs and the severe diseases they cause. Scientists spend their life digging into different factors that might help create an effective vaccine.
Inactivated vaccines:
Inactivated vaccines use the killed model of the germ that causes sickness. Actually, it doesn’t provide immunity as powerful as live vaccines. So, a person will need several doses to boost the immune system against illness. The inactivation step generally includes heating, radiation, or chemical compounds usage to break the pathogen’s genetic material stopping it from replication. To illustrate, the durability of inactivated vaccine is short in comparison to live vaccine. This is because the immune system can better recognize a bacteria or virus that actively replicates even though it doesn’t cause illness. Examples on this type of vaccine are hepatitis A and influenza vaccines.
Live attenuated vaccines:
Live vaccines come from wild viruses and bacteria. Scientists render these viruses weak in a laboratory, generally by repetitive culturing. Because those vaccines are much like a natural infection, they have the ability to replicate inside the body and create sufficient copies to stimulate an immune response. Indeed, the immune system in this case can’t differentiate an attenuated vaccine virus from a wild virus infection. Thus, live atrenuated vaccines create a strong and long lasting immune reaction identical to that produced by a natural infection. One dose of this vaccine is sufficient to build immunity in most recipients. This doesn’t deny the fact that a small percentage of recipients might not respond to the first dose, so a second dose usually offers an extra degree of immunity.
However, people with weak immune system (patients suffering from leukemia or HIV virus) or people undergoing a transplant, can’t take this type of vaccine. To clarify, the vaccine might have strong drawbacks ranging from intense to deadly infections due to uncontrollable replication of the virus. Live attenuated vaccines are fragile and easy to break or destroy by using heat or light. For this reason, it's necessart to store and treat it cautiously. Examples on live vaccines are the smallpox, rotavirus and chickenpox vaccines.
mRNA vaccines:
Researchers were analyzing and working with mRNA (messenger ribonucleic acid) vaccines for many years, and this type created covid-19 vaccines. In short, it allows the body to synthesize proteins that provoke an immune response. Also, since they don’t incorporate a live virus, they can’t inflict sickness to people. Messenger RNA is an RNA type essential for protein synthesis. Upon mRNA injection, the mRNA uses the cellular protein-making machinery to create proteins. Note that mRNA from vaccines neither enter the nucleus and nor alter the cell’s DNA. In fact, mRNA vaccines mode of action is to introduce a bit of mRNA corresponding to a viral protein into the host. As a result, this allows the immune system to acknowledge that protein as a foreign body that must go under elimination by antibodies.
To clarify, antibodies defend the body against disease by spotting pathogens, attaching to them, and marking them for destruction by immune cells such as macrophages. Consequently, the exposure of a person to a virulent virus after receiving mRNA vaccination against that certain virus, the immune memory cells (B memory cells) and antibodies will get rid of the virus before a severe disease occurs.
Toxoid vaccine:
In this type of vaccine, they use a dangerous toxin made by the germ itself that causes illness. Toxoids form from suppression or inactivation of toxicity in purified exotoxins via heat or formalaldehyde. Vaccination with toxoids can create an immunity to the pathogen components. In other words, the immune reaction main focus is on the toxins behind the illness rather than the entire germ. Several doses must be taken to boost the immune system against illnesses. Manufacturing of toxoid vaccines should be strictly under control to reach inactivation without excessive modification of the antigenic epitope shape. Example on this type is tetanus vaccine.
Conjugate vaccine:
Conjugate vaccines compromise only portions of the pathogens they defend against. These vaccines use simplest part of a target pathogen to provoke an immune response. This could be accomplished by separating a specific protein from a pathogen and providing it as an antigen on its own. First, a gene coding for a protein important for the vaccine is inserted into another virus, or into producer cells in culture. Second, the protein of interest is under creation as the carrier virus replicates. The result of this approach is a recombinant vaccine. Upon injection, the immune system will recognize the expressed protein and provide future protection against the virus.
To elaborate, conjugate vaccines fairly resemble recombinant vaccines, they’re made using a combination of 2 unique components. However conjugate vaccines features portions from the coats of the microorganism. Those coats are chemically connected to a carrier protein, and the mixture works as a vaccine. Such type of vaccines is vital to create a greater effective combination of immune response. Generally, the piece of pathogen alone can’t generate a robust immune response, while the carrier protein would. For example, influenza vaccine is of the conjugate type.
Viral vector vaccine:
Viral vector vaccines use an altered version of a virus as a vector to deliver protection. They differ from other traditional vaccines because they don’t really include antigens but rather use cells’ body to provide them. This is the case of Covid-19 viral vector vaccine which are injected in the upper arm muscle without causing any infection (harmless virus). Indeed, it enters the muscle cells and use their machinery to produce spike protein that appears on the surface. This can trigger an immune reaction to spike proteins by producing antibodies protecting people from future infection. The benefit is that we will get future protection without ever having extreme consequences from covid-19.
Future vaccine developments:
Many technologies under improvement will enhance the effectiveness of vaccine shipping and make it less complex. To make vaccines that are sufficient in one dose, it must be very effective in order to trigger efficient immune response. Technologies and adjuvants which can eliminate the need for more than one dose are still under development.
Most successful vaccines defend against acute and short durable infections mainly via the production of antibodies. Vaccines against long-lasting infections, such as HIV and Malaria, are still very challenging. One main motive of these vaccines is to activate cell mediated immune response (involving T-cells) instead of humoral immune response (involving antibodies). Advances in vaccine technology are important to limit and prevent infectious diseases which nevertheless account for 40% of deaths globally. By modifying current vaccines, new vaccine technology and methods emerge generating new vaccines to overcome this ongoing mission and save lives.
References:
-Andre, F. et al. Vaccination greatly reduces disease, disability, death and inequity worldwide. WHO (2011).
-Rappuoli, R., Mandl, C. W., Black, S. & De Gregorio, E. Vaccines for the twenty-first century society. Nature Reviews Immunology vol. 11 865–872 (2011).
-CDC “Vaccines”
-Sciencedirect “Toxoid”
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