5 questions about vaccines answered in 3 minutes

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November had been a month of vaccine news.

Based on preliminary results, Pfizer-BioNTech, Moderna, and Oxford-AstraZeneca have each reported candidate COVID-19 vaccines demonstrating at least 90% efficacy.

Here, ISTS answers five critical questions about vaccines and the new generation of vaccines – all in three minutes.

1. How do vaccines work?
Vaccines train the immune system to recognise and attack a virus by imitating an infection without causing illness.

Beyond the individual, vaccines also boost herd immunity. When a large percentage of people are vaccinated, their immunity protects other members of the local community from the disease by breaking chains of infection.

2. How are vaccines developed?
Vaccine development usually takes at least a decade, with the fastest being four years. Development occurs in three parts:

Research – Working on various vaccine designs to safely introduce the pathogen into the body’s immune system.

Testing – Three phases of clinical trials are done, with an increasingly larger pool of participants to determine its safety, side effects, dosage, delivery, and efficacy.

Manufacturing – The vaccine production pipeline is developed, usually done in parallel with research and testing.

3. What’s in vaccines?
Vaccines traditionally use inactivated or weaker versions of the virus, or fragments of the virus itself. As this requires the manufacturing of the actual virus, making these vaccines is a time-consuming process.

As a workaround, the three candidate COVID-19 vaccines trick the body into producing viral proteins of its own. In the vaccines are genetic instructions for the creation of the spike structures found on the surface of the coronavirus.

The crown-like spikes found on the surface give coronaviruses their name.

4. How are these COVID-19 vaccines special?
Moderna and Pfizer-BioNTech are producing messenger RNA (mRNA) vaccines, the first of its kind. mRNA is a small set of genetic instructions for making a specific protein.

Snippets of SARS-CoV-2 mRNA are enclosed in fat bubbles and injected into the body. Human cells read these mRNA instructions and make copies of the spike proteins. The immune system is triggered, producing antibodies that destroy the infected cells. Memory cells that remember the pathogen are created, priming the body to fight the virus when it reencounters the same spikes.

The Oxford-AstraZeneca vaccine is a chimpanzee adenovirus-vectored vaccine. Adenovirus is a group of common viruses that causes a wide range of illnesses, from the common cold to diarrhoea. Adenoviruses have previously been used in human vaccines for malaria, HIV and Ebola.

Oxford-AstraZeneca used a cold virus that usually infects chimpanzees, and genetically modified it to be harmless to humans. The adenovirus acts as a vector (biological carrier), carrying the genetic blueprints of the spike protein. Researchers chose a chimpanzee virus to prevent our immune system from attacking it, as we do not have pre-existing antibodies to the adenovirus.

5. How are these vaccines different?

Price~3 USD~37 USD~20 USD
StorageIn a regular fridgeBelow -20°C
Up to 30 days in the fridge
Below -70°C
Up to 5 days in the fridge

These vaccines all require two doses to reinforce its efficacy. However, Singapore’s Lunar COV19 vaccine candidate, with Phase 3 trials commencing next month, might be effective as a single dose.

The approval and production of these modern vaccines are currently expedited to be delivered globally. These breakthroughs in vaccine technology are incredibly compelling, not just for the COVID-19 pandemic, but also in unlocking new possibilities for future vaccines. 

Measles, smallpox, mumps and polio are just some examples of diseases that we have practically eradicated through vaccination. With 90% efficacy, far higher than what most scientists expected, these COVID-19 vaccines may be our way out of the pandemic. Even so, issues like distribution and long-term immunity may pose barriers to establishing herd immunity. What do you think are the vaccine challenges that lie ahead of us?

Written by Kow Zi Shan
Illustrated by Lim Daphne


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