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Understanding Different Types of Vaccines

A vaccine is a substance used to trigger the production of antibodies, to provide immunity against infectious diseases. They are not a cure, but a form of prevention. So, becoming vaccinated is the same as applying sunscreen before going to the Sahara, or spraying repellent before trekking in the Amazon.

Measles, Polio, SARS, Covid-19: the similarity between all these outbreaks is the use of vaccinations. But do we really know what we’re shooting up our bloodstream, and how they roll? Here’s a breakdown of the different types of vaccines, for both viral and bacterial infections.
Different Vaccine Types (WHO, 2021)
A. Live Attenuated Vaccine
This contains an active but weakened version of the virus, which stimulates a powerful immune response from the body. The presence of viral particles will stimulate the body’s white blood cells to create antibodies. The antibodies then bind to viral antigens so that white blood cells recognize, engulf & devour the virus.

Examples of attenuated vaccines include those for Cholera, Shingles and Tuberculosis.

Although these are rare instances, when a community does not reach herd immunity quickly, the attenuated virus may mutate into more infectious strains while reproducing. Still, attenuated vaccines are thankfully inexpensive with little dosage, and most importantly, provide lifelong immunity.

B. Inactivated Vaccine
In contrast to attenuated vaccines, this contains viruses or bacteria that are deliberately multiplied and then destroyed, to prevent them from spreading in the human body. Examples include the Injected Polio Vaccine (IPV), Hepatitis A Vaccine, and Pertussis Vaccine for whooping cough in children.

Inactivated vaccines trigger a weaker immune response than an active (attenuated) vaccine containing a live pathogen. However, this is great for the elderly and patients whose immune system may not be strong enough to withstand live viruses.

Inactive vaccinations will require more doses to achieve the same effect. This gives birth to “booster shots”. Boosters gradually strengthen immunity against the virus over time.

C. Live Vector Vaccine
A viral vector is an altered version of a virus that contains no antigens on its surface. Antigens are molecules found on the surface of viruses, and they bind to antibodies to trigger the body’s immune response. Then again, viral vectors have genes that will code for antigens when injected into the patient. The body reads this genetic code, and produces the viral antigens in the body. The code vanishes after a day or two, just like how our Snapchat stories disappear after 24 hours. This elicits an immune response as antibodies are created to combat the antigens.

Examples of viral vectors include Influenza, Ebola & Zika. For COVID-19, the adenovirus is currently used for live vector vaccination.
D. Messenger RNA (mRNA) Vaccine
Messenger RNA (mRNA) is a sequence of bases transcribed from our DNA. It is translated by ribosomes in our cells to produce useful proteins for our body. Our mRNA is thus like a recipe for our ribosomes to follow and cook a dish for us.

The vaccine deliberately introduces modRNA (synthetic mRNA of a pathogen) to our protective cells, which then produce the proteins that would typically be made by virus/ bacteria. This will signal our immune system to destroy the virus, if the virus is present in the patient.

In Gordon Ramsay’s terms, our vaccine’s mRNA is a bad recipe harmful to our body, but our ribosomal chefs still cook the dish anyway. Our bodies will not eat it, but our white blood cells will, since their role is to clean up all the “bad dishes” that are meant to harm our body.

In our world today, the most important mRNA vaccines are the Moderna COVID-19 Vaccine and Pfizer-BioNTech COVID-19 Vaccine.

E. Toxoid Vaccine
Similar to the first 2 types, a toxoid is an inactivated and weakened toxin. However, toxins are produced by and for bacterial infections, not viruses.

The most common bacterial infection that can be treated by toxoid vaccine is Tetanus.

F. Subunit and Conjugate Vaccines
These vaccines require only a segment of the virus/bacteria to fight it. Subunits, as its name suggests, can refer to a fragment of proteins produced by the pathogen. Conjugates form when a weak antigen joins a strong antigen carrier to fight a pathogen. Take the movie Inside Out for an example. After striving to be independent the whole day, Joy eventually works with Sadness to restore Riley’s core memories, resisting the temptation of running away and instead reconciling with her parents.

Examples of infections that require these vaccines include Human Papillomavirus (HPV), and Haemophilus Influenzae Type B (Hib).
The Reunion (Inside Out, 2015)
There are many kinds of vaccines, and there will probably be many more in time to come. Each type of vaccine undoubtedly has its boons and banes. However, the one truth that stands firm is that the risks of every vaccine decreases with more vaccinated people. Let us thereby do our part to achieve herd immunity and create a healthy, vaccinated community!

Gwen Cheng, Author
Gwen is an alumnus of Anglo-Chinese School (Independent) who currently seeks to pursue healthcare in university. Her hobbies include binging sappy romance dramas, spewing nonsense with her girlfriends, and jamming on the piano and guitar.

She wishes readers will view healthcare not as a nerdy boredom, but as an essential humane aspect that can be appreciated, just as she has come to realize. You can find out more of her musings on her personal blog, Frozenmidair.