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How Does The COVID Vaccine work?

Author: Dr. Rohini R

Vaccines train a person’s immune system to recognize and fight against specific germs that can cause serious illness. COVID-19 vaccines work with the immune system to help develop defenses to the disease so that the body will be ready to fight the coronavirus if exposed to it in the future.  If the vaccinated person gets exposed to coronavirus in the future, the antibodies will fight the virus and prevent COVID-19. 

How COVID-19 Vaccines Work

Many types of vaccines have been developed for COVID-19. The common goal of all vaccines is to trigger an immune response that is specific to the COVID-19 coronavirus.  Although all of the COVID-19 vaccines aim to achieve protection from COVID-19, they use different methods. 

Most COVID-19 vaccines use the coronavirus spike protein to cause immune response.  The coronavirus that causes COVID-19 has spikes of protein structure called S protein on the surface of the virus. These spike proteins help the virus to attach to cells and cause the disease.  

Our immune system recognizes this spike protein as foreign and produces long-lasting immune cells and antibodies (fighter cells) that stay in the blood and protect the person. If a vaccinated person is exposed to the coronavirus at a later time, their immune system will respond faster and more effectively to fight against the virus. The vaccinated person gets protection against the disease without getting sick.  

What are the Types of COVID-19 Vaccines? How Do They Work?

  • Messenger RNA or mRNA Vaccines

COVID-19 mRNA vaccines use a genetic code called RNA. After vaccination the RNA gives instructions to the cells to begin producing harmless spike protein pieces and display them on the cell’s surface.  The body’s immune system recognize the spike protein as foreign and begin building an immune response and making antibodies.

mRNA vaccines are available as two dose vaccines.  Pfizer-BioNTech and Moderna COVID-19 vaccines are messenger RNA (mRNA) vaccines.

  • Viral Vector Vaccines

In this type of vaccine, genetic material from COVID-19 virus is inserted into a weakened live virus, such as an adenovirus.  After vaccination, the weakened virus known as viral vector enters the cells. It delivers the genetic material from the COVID-19 virus which gives instructions to the cells to make harmless copies of coronavirus spike protein. Once the cells display the spike proteins on their surfaces, the immune system recognizes the protein as foreign and responds by creating antibodies and defensive white blood cells.  

Vector vaccines are available as one dose vaccine. Oxford-AstraZeneca, Sputnik V and Johnson & Johnson -Janssen COVID-19 vaccine are viral vector vaccines.

  • Protein Subunit Vaccines

Protein subunit vaccines use non-infectious harmless protein component of coronavirus directly, usually the spike protein. This protein which is found on the surface of the virus is manufactured in a laboratory.  When the vaccine enters the body, immune cells recognize the spike protein as foreign and begin building T-lymphocytes and antibodies. 

The Novavax COVID-19 vaccine is protein subunit vaccine.

  • Inactivated vaccines

Unlike the other vaccines, inactivated vaccines contain the entire coronavirus which has been chemically modified to make it inactivate. Usually a chemical called beta-propiolactone is used to inactivate the virus in the vaccines. 

This type of vaccine do not produce long lasting strong immune reaction as other vaccines.  Adjuvants may be used in the inactivated COVID-19 vaccines to generate a stronger immune response. To provide immunity in the long run, booster shots may be necessary. 

Sinovac, Sinopharm, and Bharat Biotech COVID-19 vaccines are inactivated vaccines.

Why should you take the COVID-19 vaccine?

COVID-19 vaccine helps protect people in the following ways:  

  • Helps in preventing COVID-19 
  • Reduces the chance of getting seriously ill and hospitalized if a person gets COVID-19
  • Lowers the risk of dying from COVID-19   
  • Makes it harder for the disease to spread as the number of people who are protected from COVID-19 increases, thus contributing to herd immunity
  • Prevent COVID-19 virus from spreading and replicating, which allows it to mutate

Does The Covid Vaccine Work?

For a single dose vaccine, it typically takes about two weeks after the vaccination for a person to have significant levels of protection. 

For two-dose vaccines, both doses are required to provide significant immunity. It typically takes about two weeks after the second dose of vaccination for a person to become protected. 

Is the COVID Vaccine safe?

COVID-19 vaccines are safe for most people older than 18 years. Common side effects that occur after vaccination are sore arm and sometimes mild fever, flu like symptoms, tiredness and headache occur for a day or two.  These symptoms are normal and are signs that the body is building immunity.

If a person has any of the following conditions it has to be discussed with the doctor:

  • History of severe allergies, particularly to any vaccine
  • Compromised immune system
  • Pregnant or nursing 

Effect of COVID-19 Vaccines against Variants

The COVID-19 vaccines are expected to provide protection against new virus variants or mutation. The COVID-19 vaccines create a broad immune response. Any new changes or mutations of the virus would typically not make the vaccines completely ineffective. 

Should a person already infected take the vaccine?

It is advisable to take the vaccine because as it is not known how long the natural immunity might last. Available data suggests that neutralizing antibodies wane off in 3 to 5 months. 

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