How vaccines work with immune system to protect us from infection?

A vaccine is a type of medicine that is designed to stimulate our immune system against a specific pathogen, such as a virus or bacterium, so that we are protected from illness if we come into contact with that pathogen in the future. Vaccines have an important role in protecting us from infectious disease. 

But how do the vaccines work? 

Well, put simply, vaccines train our immune system to detect and attack pathogens. Here is a little explanation of how they do it, from start to finish. 

Our immune system is incredibly impressive..! It is a marvellously complex network of molecules and cells, which has the power to destroy pathogens like viruses and bacteria. There are two general sides of the immune system coin the innate immune system and the adaptive immune system. You're born with an innate immune system that is essentially ready to roll and you develop your adaptive immune system over time by exposure to various pathogens. The innate immune system is rapid and non-specific. 

The part of the immune system that vaccines train is  adaptive immune system. It’s first job is to recognize an invader. In the case of this bacterium it does this by detecting molecular markers called antigens, that are part of all pathogens. After detecting an antigen, the adaptive part of the immune system starts mounting a bespoke response. 

B-cells convert to plasma cells, and start creating proteins called antibodies, which bind specifically to the antigen. Together with immune cells called phagocytes, antibodies can destroy the pathogen. The adaptive immune system also produces Killer T cells, which have the ability to detect and destroy cells infected with the pathogen. 

But it doesn’t end there - to prevent against future infections, the adaptive immune system also has a memory. It produces long lived memory cells, which lie in wait ready to pump out the right antibodies and killer T cells if the same pathogen is ever seen again. This is called immunity. 

Vaccines work by activating the adaptive immune system and so creating immunity. They safely introduce antigens for the immune system to train on, preparing itself to fight real infections in the future.

So what actually goes into a vaccine?

Well, there are several different types. 

One of the most common are called live-attenuated vaccines. These include things like MMR (measles, mumps, and rubella combination vaccine) or BCG (bacille Calmette-Guerin---a vaccine for TB). Live attenuated vaccines work by introducing a weakened version of a living pathogen into the body. These attenuated pathogens are not strong enough to cause disease in people with healthy immune systems, but they can still trigger a strong immune response. Live attenuated vaccines trigger a similar immune response to a real infection, leaving behind the same memory cells. This means that some can provide a life-time of protection after just one or two doses. 

Another key type of vaccine is called a subunit or recombinant vaccine - they work differently. Instead of a live sample, subunit vaccines contain only part of the pathogen. For instance the vaccine for Human Papilloma Virus, HPV uses hollow virus-like particles made from a protein found in HPV. Alone, these subunits cannot get the immune system’s attention, and so they need a bit of help from another ingredient - an adjuvant.

Adjuvants wake up the immune system, triggering it to see the subunit antigens and start creating antibodies and memory cells. Subunit vaccines contain no live pathogens, and so lack the genetic information needed to replicate. That means that they are not infectious and are safe even for people with weakened immune systems.

But generally, they don’t trigger the production of as many memory cells, compared to live attenuated vaccines - and so they don’t provide such long lasting protection. Training the immune system through vaccination helps to protect individuals from infection. But vaccines can also protect people who can’t receive them. This is called herd protection or herd immunity.

Herd immunity is created when a large percentage of a population is immune to a disease. It works by disrupting chains of infection. Without new hosts to infect, pathogens can’t survive. That means that if a pathogen tries to infect someone who is vaccinated and so immune, it dies and the chain of infection is broken. 

If enough chains are broken in a population, it becomes very difficult for pathogens to reach those who would be vulnerable. Herd immunity protects millions of people around the world, but if vaccination rates drop, there is a risk that diseases can reappear. For example, measles was declared eradicated in the United States in 2000, but since then, falling vaccination rates have led to a resurgence of the disease with outbreaks recorded in 31 states. 

If herd immunity is maintained for long enough though, diseases can be eradicated completely. For example smallpox, which is estimated to have killed 300 million people in the 20th century, is now considered extinct. 

All thanks to vaccination, its training regime and the wonders of herd immunity.

 STAY SAFE AND GET FULLY JABBED AS SOON AS POSSIBLE..!