Vaccine, Discovery and Types

What are Vaccines – Discovery & The Four Main Types

Vaccines contain the same germs that cause the disease.

Center of Disease Control (

Yes, they are right, but what they went on to clarify is that vaccines contain either weaker strains or dead cells of the pathogen. A vaccine makes your body behave as if there is a disease and simulates the anti-body behaviour and subsequently creating an immunity to the disease because now your body knows how to fight it off.

The major difference between vaccine and medication is that medication is a cure while the vaccine is prevention to the disease itself.


First vaccine

In the 1790s, there was a rumour that Cowpox disease protected dairymaids against smallpox, it was seen with many cases that this would be true. Edward Jenner found interest in this matter during his apprenticeship with George Harwicke. Jenner pondered over the matter and concluded that cowpox could be used as a source of protection from smallpox by deliberate transmission. He, in May 1976, met a young a dairymaid, Sarah Nelms, who had a fresh case of cowpox lesions on her hands and arms.  Using matter from the lesions of Nelms, Jenner inoculated an 8-year-old boy, James Phipps. Subsequently, James developed a fever and mild discomfort in his axillae, but nine days later he felt cold and lost appetite but was better the next day. In July, Jenner took a risk and completed the experiment by inoculating the boy once again but this time with fresh smallpox lesions. The boy was safe and did not develop any smallpox leading to the first-ever successful experiment with the smallpox vaccine.
Source: National Center for Biotechnology Information

How the immune system defends against contagious diseases

When a foreign pathogen invades us, our body’s immune system starts to respond, it starts to identify and remove the pathogen from our body. Signs that it is working are:

This also triggers our second line of defence – Adaptive Immunity. Special cells called B Cells and T Cells start fighting the microbes.

They also start recording information about the pathogen. Information like what the pathogen looks like and how to fight the pathogen in case if the attack happens again.

But the problem with this response system is that this happens after someone gets sick, so it is great for the second time we get sick but for the first time, not so much.


Vaccine, on the other hand, works to get the body ready before an actual attack from the disease. A vaccine is used to trigger the Adaptive Immunity response of the body without infecting the body to the actual disease. This means that we get all the information about the disease without actually getting ill.

Types of Vaccine

Live Attenuated Vaccines

Live Attenuated Vaccines are made from the pathogen itself, but a much weaker strain. But due to the ‘live’ nature of the vaccine, they are difficult to make. They are created for both bacteria and viruses but are more common for viruses.

Live Attenuated Vaccine generates a response similar to the infection, as the strain is in actuality the pathogen itself, but without causing the illness. But that has its own risks and it is not possible to give these vaccines to someone with a weak immune system as it risks them to get the full-blown disease. But on the upside, as the strain is so close to the actual pathogen, that it makes for a great long-term immunity.

Inactivated Vaccine

Inactivated Vaccines are dead pathogen cells used to trigger the Adaptive Immunity response. These were among the earliest forms of the vaccine developed by modern science.

They are much easier to make and also have far lesser side effects than the Live Attenuated Vaccines but they don’t have a long-lasting effect. On the plus side, they can be made for both bacteria and viruses.

Subunit or Conjugate Vaccines

An antigen is the part of the pathogen that triggers the immune response, and this is what Subunit Vaccines are made from. Scientists have figured out the way to segregate the pathogen into its core parts and use only the antigen as a part of the vaccine that they develop. This has reduced the risks that Live Attenuated Vaccines pose for individuals with lower immunity but has the same long term effect.

By further segregation of the antigen, scientists can trigger specific immune responses and not the entire series of Adaptive Immunity Response. Usually, a specific protein or carbohydrate is segregated and used in the vaccine to generate a specific immune response.

DNA Vaccines

Still in the research phase for human use, DNA vaccines are the latest form of vaccines to be developed. The idea here is to make a vaccine that would contain the DNA coding of the antigen that we want the body to develop an immune response against. This means that the body would never be exposed to the actual pathogen, making it very safe for people with a weak immune system.



Vaccines are one of the greatest discoveries of mankind that have led to the protection of devastating diseases like polio, measles, smallpox, etc. It is the hope that we get when we look at the new dangers of the modern world diseases like Covid-19, that one day we shall have a vaccine against this as well. Though very complicated to make, but if we have the vaccine to our diseases, we could very well be looking at an illness-free life in the future.

As always, Thanks for Reading.