Covid-19 vaccines, all we need to know (Simplified)-Part 1

The story of the vaccine started in a small market-town of Berkeley (Gloucestershire) in the UK back in 1796 when Edward Jenner inoculated vaccinia virus (cowpox) onto young James Phipps to demonstrate immunity against smallpox. The efficiency of his work has enabled the development of the world’s first vaccine against smallpox in 1798, but do you know that the immunization has been in practice hundreds of years before Edward Jenner’s work came to the limelight? It was Buddhist monks in China who used to drink snake venoms to confer immunity against snakebite and smear wounds with cowpox to confer immunity against smallpox. This smearing technique is known as variolation which was later established as vaccination by Edward Jenner.

Edward Jenner (1749–1823)

The development of the vaccine was considered as one of the greatest medical advancements of all time in human history with an estimated 8 - 10 million lives are presently saved on an annual basis worldwide. Diseases such as smallpox and rinderpest (deadly bovine disease causing the deaths of cattle herds throughout Europe and Africa from the 18th to the 20th century) was successfully eradicated from the earth’s surface while polio, tetanus, hepatitis B, hepatitis A, rubella, measles, whooping cough (pertussis), pneumococcal disease, rotavirus, mumps, chickenpox, and diphtheria were kept at bay with successful vaccination programmes globally.

Cows died due to rinderpest

Source: https://upload.wikimedia.org/wikipedia/commons/3/36/Rinderpest_1896-CN.jpg

Despite its extraordinary achievements, many conspiracy theorists had spread ill-testimonies against vaccines which had consequently created countless panics among the public. This has further dented with the Covid-19 outbreak. As scientists around the world are working hard to find the cure, the closes solution that we have at our disposal for Covid-19 is the vaccine. The vaccine can never cure a disease, but it boosts our immune system to fight against the virus.

I made a poll and based on the outcomes, this write-up is catered to explain how the vaccine works, how safe is vaccination, and when we would achieve herd immunity with the current vaccination rate in Malaysia.

To begin with, let us briefly review the type of Covid-19 vaccines approved under the National Covid-19 immunisation programme. There are six vaccines all together: Pfizer, AstraZeneca, and Sinovac were widely administered to Malaysians while Sinopharm, Johnson & Johnson and CanSino were approved for emergency use. There is another vaccine currently in a clinical trial in Malaysia, the Chinese Academy of Medical Sciences Inactivated (Vero Cells). How do these vaccines work individually, we can review them in another blog. However, this write up is mainly to give an overall idea of how the Covid-19 vaccine protects us in general.

Pfizer/BioNTech BNT162b2

Oxford/AstraZeneca AZD1222

Sinovac CoronaVac

Sinopharm (Beijing) BBIBP-CorV

Janssen (Johnson & Johnson) Ad26.COV2.S

CanSino Ad5-nCoV

Chinese Academy of Medical Sciences Inactivated (Vero Cells)

Types of vaccines

Source: National Covid-19 Immunisation Programme handbook

Firstly, we must understand how our immune system helps to fight illness before getting to understand the mechanism of vaccines in protecting us. We are generally exposed to thousands of germs (bacteria, viruses, parasites) every day and some of these germs can breach past the skin, invade our body, and may cause illness. As a counter-reaction, the body’s immune cells (e.g., macrophages, T-lymphocytes, B-lymphocytes) will fight against the invading germs and clear them off from the body.

The most important immune cells are the T-lymphocytes and B-lymphocytes, both of which belong to the adaptive immune system. As the macrophage act as the first line of the defence system (innate immune system), they will swallow (engulf) these germs and breakdown into small pieces known as antigens.

1. Macrophage engulf the virus.

2. Virus are attacked, processed and broken into pieces (antigens).

3. Antigens leaving macrophage to be recognized by the B-lymphocytes.

The limited B-lymphocytes in our body recognizes these antigens, multiply (clonal selection) and produces antibody against the antigen. As the antigens are part of the germ, thus, the antibody produced by the B-lymphocytes can now attack the germs, in the case of Covid-19, it attacks the SARS-CoV2 virus.

1. B-lymphocytes recognizes the antigens from the macrophages.

2. B-lymphocytes making clonal selections and multiply into plasma cells.

3. Plasma cells (a kind of B-lymphocytes) specialised to produce specific antibody against SARS-CoV2 virus.

4. Some B-lymphocytes will become memory cells.

On the other hand, the T-lymphocytes will attack the infected cells in our body, and some will kill the infected cells. After clearing the germs from the body, some T-lymphocytes will become memory cells too.

1. T-lymphocytes initiate attack against cell infected by SARS-CoV2 virus.

2. Infected cells are killed.

When a person is infected by the SARS-CoV2 virus, it will take several days for the immune cells to recognise the virus, multiply (clonal selections) and finally fight the virus. This is the reason why we develop an illness upon infection despite possessing immune cells. After the infection, memory cells will be developed. The function of the memory cell is to remember what it learned about how to protect the body against that disease and should the same virus infection happen again, the antibody production against the virus will be more efficient.

An analogy that we can use here is when terrorists attack a country without any alert, they would be conquering some areas. When the army is deployed, they will fight the terrorists and recaptured those areas from the terrorists. After the terrorist attack, the army and its leaders would remember and learnt how to protect the nation against such incidences should they happen again. If the army is weak, then the country would fall into terrorists' hands forever. This is how the immune system works in our body too.

1. SARS-CoV2 virus infection occurs.

2. Antibody production against the virus take time few days to weeks to peak.

3. After successfully defeating the viruses, plasma cells producing antibody will die (apoptosis), however some will become the memory cells. Thus the antibody level will drop.

4. The SARS-CoV2 virus (same variant) infection for 2nd time.

5. Since the memory cells learnt about the infection, the antibody production is faster and produced at greater magnitude (more efficient) this time.

As there are different types of vaccines available, they work in different ways however the fundamental aim of vaccine is to develop the memory cell without the actual infections. The mRNA, non-replicating viral vector or the inactivated virus are not the real viruses. They have been treated and modified into the vaccine, thus it does not replicate or incur any harm when injected into the human. It is merely a simulation that prepares the immune system and most importantly it must be able to develop the memory cells.

An analogy will be the movie Matrix. When Neo was introduced to the simulation world, he would be able to Kung Fu with Morpheus though he had not learnt in the actual world. It’s the simulation programme that enables him to acquire such skills. A vaccine is like a simulation programme in the movie Matrix. Without actual infection, the immune cells are learned to produce memory cells with vaccines, so that when real virus infections occur, the antibody production will be faster and at greater magnitude to fight the viruses.

Just like the antibody production by the immune cells take few days to weeks after infection happens, the vaccine also takes few days to weeks to stimulate antibody productions. Thus, it is possible for a person to be infected by the virus just after the vaccination as the antibody production is not peaked yet.

1. 1st dose of vaccine administration.

2. Antibody production reaching peak.

3. Some vaccines (inactivated vaccines), the 1st dose does not provide as much immunity as possible, thus it require a 2nd dose to build more complete immunity.

4. 2nd dose (booster) of vaccine administration.

5. Larger magnitude of antibody is achieved after the 2nd dose of vaccine is administered.

References

1. N.A. Malaysia – COVID19 Vaccine Tracker. (2021). Available at: https://covid19.trackvaccines.org/country/malaysia/. (Accessed: 4th August 2021)

2. N.A. National Covid-19 Immunisation Programme: The Special Committee for Ensuring Access to Covid-19 Vaccine Supply (JKJAV). (2021).