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Health and Fitness,  Science

The Tale of Vaccines: Why it Take So Long to Make One

What is the most popular question all over the world at this moment?

You know it. Maybe even you have asked this question several times.

When will we get the coronavirus vaccine?

You never had an interest in vaccines like this before. Because a vaccine is need of the hour. The whole world is working to get that one vaccine and billions of people are praying for that.

If you are not from medical science background, some common queries you might have is-

What the hell is a vaccine and how can it protect us?

And most importantly, why it take so long to make one vaccine?

So today let’s find out the answers to these questions and dig deeper into the world of vaccines.

Before discussing vaccines, we must know our bodies defense mechanism and how it works.

How does a virus or bacteria make us sick?

A bacteria after inserting into the body releases toxins that make us sick (I am talking about bad bacterias, there are good bacterias as well and our body contains billions of those).

Whereas, a virus after entering into the body inserts its genetic material into our own cells, causing those cells to burst or die.

The antigen is an important aspect in this respect. An antigen is any substance that is capable of stimulating an immune response, which might be a part of a virus.

You must have heard about the immune system of our body, it works exactly like the defense sector of a country. The immune system is of two kinds, Native and adaptive immune systems.

Innate immune system’s work is to identify pathogens (virus/bacteria) and stop them from inserting into our body. Our skin, muscles try its best to kick out pathogens as soon as they identify them.

Think of the native immune system like an army of a country that is protecting their country from terrorists.

Even then, if a pathogen then enters into the body, our adaptive immune system kicks in. It reacts in a very specific way to specific pathogens.

Our body has antigen presenting cells (APC), which are produced in our bone marrow. When APCs encounter any pathogen, it sends signals to other cells (which are our weapon cells) such as T cell, B cell, which together attacks the invader pathogen and kills it.

Once our adaptive immune system wins over the pathogen, it creates memory cells in our body for future protection from the same pathogen.

That means, if the same virus/bacteria again attack us in the future, our body would have weapons ready for them (in the form of memory cells) and can kill them in no time. That’s why small children are so prone to disease (they don’t have memory cells).

Sound great right! How amazing our body is. But the whole process described above takes time. By that time, many pathogens (not all) can mutate at a rapid rate and can hijack our immune system.

And if you have a weak immune system, then pathogens would have an extra advantage to invade your body.

That’s where vaccines come into the picture. Basically it leverages the immune response of our body to fight infections.

Let’s go back in time to get the bigger picture about vaccines.

Smallpox was one of the most dangerous viruses in earlier times. Millions of people used to die due to smallpox. It started in ancient India, China, and in the middle east around 1000 CE.

People that time used to scratch smallpox sore in the skin and then blowing that smallpox matter into nostrils of people to combat smallpox (as the image below). This is known as variolation


Buddhist monks (and many others) used to drink snake venom to confer immunity to snake bite. You might have heard stories like that. This emphasizes that although people might not aware of vaccines at that time, they used similar concepts to treat viruses as we do today.

The first discovery of vaccines dates back to 1796 by Edward Jenner, an English physician. The discovery itself has an interesting story.

Edward Jenner noticed something interesting in a dairymaid. The dairymaid said- ‘I shall never have smallpox, for I have had cowpox‘.

Cowpox was also a viral infection, similar to smallpox but infected cows (humans could get the disease from cows).

Later Edward Jenner realized, the woman was correct. People who have had cowpox never developed deadly smallpox.

So, he decided to investigate if the cowpox virus could be used to treat smallpox.

Edward Jenner collected cowpox virus and inoculated an eight-year-old boy. After a few days of fever, the boy recovered. Two months later, he inoculated the boy with dangerous smallpox virus. But nothing happened to the boy.

That’s how Edward Jenner found a cure for smallpox disease.

Edward Jenner joyexcel
Edward Jenner

What actually happened?

When a virus infects an unfamiliar host (in this case cowpox virus inserted into an unfamiliar human body), it is less dangerous. So the cowpox virus didn’t harm the boy.

At the same time, the virus stimulated memory cell production by the immune system which can protect from smallpox virus.

Although, the concept we use today to invent vaccines is given by Louis Pasteur in the 18th century, who discovered vaccines of chicken cholera, anthrax, and rabies.

By this time, you already have got an idea about vaccines. Let’s explore vaccines some more-

How would we define a vaccine?

In scientific terms, a vaccine is defined as

“Suspension of live (usually attenuated) or inactivated microorganisms (e.g., bacteria or viruses) or fractions thereof administered to induce immunity and prevent infectious disease or its sequelae”.

Attenuated means weakening the pathogen by applying heat or chemical on it.

Unlike medicines that treat disease, vaccines work by preventing the disease in the first place. The immune system triggered by a vaccine produces the same memory cell that a true virus would. But as the pathogen present in the vaccine is inactive or weak, it can’t harm us.

How do vaccines are made?

There are various ways to make a vaccine. It depends on the pathogen for which one tries to make a vaccine.

Below are some of the different types of vaccines

1. Live-attenuated vaccines

This kind of vaccine contains a weakened form of pathogens that causes a disease to assist in building immunity. The pathogen made weak by applying heat or chemicals. This type I already discussed above.

Just one or two doses of such vaccines are enough to build a lifetime of immunity against a disease. However, since it contains live pathogens, it can not be given to people with weaker immunity.

Some examples of such vaccines are- vaccinia (smallpox vaccine), measles, mumps, rubella (MMR vaccine), varicella (chickenpox vaccine), etc.

2. Inactivated vaccines

These vaccines contain an inactivated pathogen that can not cause disease. Even though inactivated, but the antigen present in the pathogen is enough to trigger memory cell formation in the body against the disease.

Since it contains an inactive pathogen, it requires several dosages of vaccines time and again to combat the virus/bacteria. People with compromised immunity are also safe with these vaccines.

Examples are polio vaccine, rabies vaccine, Hepatitis A vaccine, etc.

3. Toxoid vaccines

This type of vaccine doesn’t contain any pathogen, instead, it contains an inactive toxin. The toxin released by the pathogen (and cause disease) is made inactive by applying chemicals and then used as a vaccine.

In this case, vaccines create immunity to the parts of the pathogen not to the whole pathogen. The immune response is targeted to the toxin instead of the pathogen.

Examples are diptheria, tetanus vaccine (DTP vaccine).

4. Subunit, recombinant, polysaccharide, and conjugate vaccines

In such type of vaccines, a specific part of the pathogen like its protein, sugar, capsid, etc. are used to trigger immunity. These small pieces of germs can not cause disease but can give a strong immune response.

These vaccines are safe even for people with weak immunity but require multiple dosages again and again.

Examples are hepatitis B vaccine, HPV vaccine, etc

Except for these, recently scientists are trying to develop gene-based vaccines. In these vaccines, genetic materials (DNA or RNA) of the virus is used to get an immune response from the body.

Such DNA or mRNA vaccines are thought to be vaccines of the future. Scientists working at this moment to develop coronavirus vaccine are relying mostly on developing these types of vaccines.

Finally the burning question

Why it take so long to develop a vaccine?

If you have read the above paragraphs, you must have understood that vaccine development is not a straightforward process. It is a trial and error process over a period of time.

What have people done to develop a coronavirus vaccine?

Scientists have determined the genetic sequence of COVID-19 (in record time).

Now, they are trying all the methods of vaccine development described above. Even if anyone claims to develop a vaccine (which you hear often nowadays), it has to go through a series of clinical trials.

1st clinical trial on healthy, normal volunteers (This is where most COVID-19 vaccines are). Once you pass it with utmost safety and no side effects then there is 2nd clinical trial on a larger population who are at risk of infection, like healthcare workers.

Even if a vaccine passes the 2nd clinical, often it is checked on people living in different climates, different races of people to ensure safety.

After all these successful trials, a vaccine is approved for widespread use. All these steps require synchronization among a large number of people. Scientists, doctors, healthcare workers, and the government have to work together to get a vaccine.

Therefore, expecting a vaccine development in 6 months is our ignorance.

Even if under intense public pressure, companies try extremely hard to develop a coronavirus vaccine, something more fatal than coronavirus can happen.

History has already taught us what can happen if we make even a little mistake in making a vaccine. If you have heard about ‘the cutter incident’, then you know what I am talking about.

In April 1955, more than 200000 children in the USA received a polio vaccine in which the virus present was not properly inactivated by a company called ‘Cutter laboratories’.

40000 children got polio along with more than 200 cases of paralysis and death. The vaccines contained live polio viruses (active virus), although it passed the safety test.

Due to this negligence, thousands of children suffered. Obviously, the company wanted to sell out its vaccines in a rush.

We are exactly in a similar situation where the probability of happening similar incidents increases. Under intense pressure from the government and public, vaccine makers might make a small mistake that can bring catastrophe.

I am not trying to scare you, just trying to convey that things like an effective vaccine take time to develop. I am very hopeful that soon we will get a vaccine for COVID-19 (Click here to read my extensive article on coronavirus).

But until then have patience, be safe, and keep learning.

Let’s take some time to appreciate the changes vaccines have brought to our lives.

Do you know how people with smallpox looked like?

To be honest, I didn’t want to upload such an ugly picture in the first place but just that you get to know about its lethalness, I am posting a picture-

Children with small pox
child with smallpox

Not only smallpox but there are many other similar diseases which are completely eradicated from the world due to invention of vaccines.

Of course, there are people who see vaccines as a danger because of their side effects. Yes, vaccines might have some side-effects like fever, pain, vomiting in the initial days of vaccination but that’s mild in most of the cases.

Even then, what if your body is not suitable for vaccination (hypothetically)?

What if you develop a serious illness because of vaccination?

In that case, you should become the biggest promoter of vaccination due to a concept known as ‘herd immunity‘.

Only herd immunity can protect an unvaccinated child or person. Herd immunity means enough people are immune to a disease (maybe due to vaccination) that it can’t spread, and dies before it reaches its victims.

To achieve herd immunity more than than 90% of people need to be vaccinated to build immunity against a disease.

We are surrounded by viruses and bacteria around us. Today it’s coronavirus, tomorrow there will be a new virus. We can not get away with pathogens.

But what we can certainly do is to understand these monster microorganisms in a better way to prepare ourselves better with advanced weapons that can kill them.

Vaccines are one of the weapons we have to combat with pathogens.

What are your thoughts on vaccines? Share them in the comment section.

Stay safe and stay well. Until next time


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  1. History of vaccination-The immunization advisory committee
  2. Healthaffairs
  3. VBI Vaccines-Louis Pasteur
  4. Vaccine types-vaccines.gov
  5. Image source: Labroots
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