Can we imagine a healthy world without vaccines?
Disease-causing germs would spread uncontrollably, putting lives at risk. Controlling outbreaks like COVID-19 would have been nearly impossible.
Vaccines are truly a gift to humanity, aren’t they?
Do you know what actually a vaccine is?
A vaccine is a substance or suspension of microorganisms which are killed, weakened, or fragmented.
The function of a vaccine is to trigger our immune system for the future attack of the microorganisms and protect our health.
Why Are Weakened or Killed Microorganisms Used in Vaccines?
The main goal of a vaccine is to trigger the body to produce antibodies against a disease without actually causing the disease itself.
If a harmful microorganism were introduced into the body without any protection, it could make us sick and harm the body badly.
That’s why weakened or killed microorganisms are used in vaccines. These versions of the pathogen are not strong enough as real pathogens to cause illness, but they still stimulate the immune system to produce antibodies. As a result, after vaccination, sometimes mild symptoms like a slight fever or body aches could be experienced by a person, which are signs that the immune system is responding to the vaccine.
This prepares the body to fight off the real pathogen if it’s encountered later.
Why can't we eat vaccines?
Vaccines are mostly pushed through injection in our blood because of the presence of WBC in blood. They identify vaccines as foreign molecules and try to destroy them. Our immune system produces antibodies against these weakened, killed microorganisms present in vaccines and knocks them down completely for the protection of our body.
If we eat vaccines, they will go to our stomach, and HCl and other digestive enzymes may damage them, and the main function—protection of the body—will not happen.
But some vaccines are taken orally. These vaccines are designed in such a way to withstand gastric acid in the stomach and are absorbed by the intestine. On the other hand, for activating immune cells in the mucosa, oral vaccines are very helpful. Oral vaccines are safer and cost-effective as well.
In the future, when the body is actually attacked by such microorganisms, already-produced antibodies activate and work against these microorganisms, defending the body like an army.
So, you can think vaccines also insert a memory card where the data of pathogenic microorganisms is inserted. This helps the immune system to create the antibodies, the army of the body.
Classification of vaccines
Inactivated vaccine
Inactivated vaccine doesn’t mean the vaccine is inactive. The pathogenic bacteria or virus particles are killed and used in this vaccine so that they lose their disease-creating ability. This type of vaccine is not very strong, so several doses may be needed. COVID-19 vaccine, Polio vaccine, Influenza vaccine, Cholera vaccine, Typhoid vaccine and Plague vaccine are examples of this type.
Attenuated Vaccine
In this type of vaccine, live pathogens are used by reducing their disease-creating power. These pathogens are cultured in abnormal conditions for years, where they adapt to survive in that abnormal environment. They become weak in normal conditions, meaning in the human body, they cannot survive properly. That’s how they become weak, and their capability of creating disease is reduced.
They are more effective even in a single dose, but there is a low possibility of causing disease in the body because all the pathogens are alive. Oral polio vaccine, Oral typhoid vaccine, Tuberculosis vaccine, etc., are examples of attenuated vaccines.
Subunit vaccine
Generally, in a vaccine, fragmented or weakened microorganisms are used. Instead of weakened pathogens. In the case of subunit vaccines, protein, peptide, or carbohydrate parts of microorganisms are used which are actually responsible for causing disease.This is why they are called “subunit” vaccines, as they contain only small, disease-causing parts of the microorganism rather than the whole pathogen. It is a type of next-generation vaccine.
There are three categories of this vaccine:
Protein subunit vaccine:
In this subunit vaccine, the protein part of pathogens is used. For example, Hepatitis B vaccine, acellular pertussis vaccine, etc
Polysaccharide subunit vaccine:
Some bacteria contain sugar capsules as their cell wall. The vaccine produced using this polysaccharide chain of the cell wall is called a polysaccharide subunit vaccine. Pneumococcal polysaccharide vaccine, Typhoid (Vi polysaccharide) vaccine, Meningococcal polysaccharide vaccine, etc., are examples.
Conjugated vaccine:
Antigens of microorganisms are also used to produce vaccines. Some poor antigens are not able to activate the immune system. So, they are covalently attached to a protein carrier and thus activate the immune system. They are known as conjugated vaccines. Pneumococcal conjugated vaccine (PnC), Meningococcal group C conjugate (MnCC) vaccine, Haemophilus influenzae type b (Hib) vaccine, etc., are examples.
Recombinant vaccine
Genetic engineering techniques apply here. First of all, a portion of RNA from a pathogenic virus is selected which may code for a spike protein. But RNA is unstable, so this mini portion is converted into DNA by reverse transcriptase.
We get our DNA; now it’s time to introduce this DNA fragment into bacteria to produce spike protein. For this, harmless carriers such as plasmids or viral vectors are chosen and cut by restriction enzymes. The DNA is inserted into the plasmid by ligase enzyme, and recombinant DNA is introduced into the bacterial cell. Because of that recombinant DNA, where information about spike protein is present, the bacterial cell produces the spike protein of the virus. These spike proteins are used as vaccines. Our body considers that spike protein as foreign molecules and produces antibodies to destroy them completely.
DNA vaccine
These vaccines do not involve recombination or genetic engineering techniques. A small portion of DNA of a virus is selected which can code for any antigenic protein. Then this DNA fragment is inserted into muscle cells of the host by a gene gun or air pressure. After entering into the host cell, this DNA fragment moves to the nucleus. After transcription and translation processes, the DNA fragment makes mRNA, which instructs the ribosomes of cells to produce that antigenic protein.
After that, the process is simple. Our body builds antibodies against that unknown antigenic protein from the disease.
By the way, this vaccine is safe and a proven effective vaccine. DNA vaccine does not need to be stored at low temperatures because of its stability compared to other protein-based vaccines. It is easy to handle and less expensive. Vaccines for influenza, human papillomavirus (HPV), and ZyCoV-D (a DNA plasmid-based COVID-19 vaccine), etc., are examples of DNA vaccine.
Edible vaccine
Many data show that almost 20% of infants worldwide and more than 2 million people died without having vaccines. That’s why, for the general public, especially for underprivileged children, this type of vaccine is produced. Antigenic proteins are inserted into some mostly available crops, vegetables, or fruits such as rice, potato, corn, banana, lettuce, etc. When this food is consumed, the protein goes inside the body.
When these antigenic proteins are introduced into the bloodstream through digested small molecules of food, they get activated and trigger our immune system to produce antibodies.
Conclusion
I think vaccine is like a coach, training our body to fight against harmful germs. Injection or edible, vaccine has changed in many ways and has crossed a long way with the intention of making beautiful and healing in mankind.
Vaccines are not just medicine—they’re a promise for a safer future.
