Types of Covid-19 Vaccines

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Vaccines protect us from infections

What are Vaccines?

Vaccines are type of medicines that are used to prevent infectious diseases.
In principle, vaccines mimic infection to alert immune system to produce antibodies.
In simple words, vaccines contain the killed or inactivated form or small piece of the same infectious agent or germ (such as a virus or bacterium) that in original active form can cause infection. The intent of the vaccination is to provide controlled exposure of the infectious agent stimulating immune system of the body to produce immune cells or antibodies.
Since vaccines do not contain active or original form of the germ, they are unable to cause infection.
Many new generation vaccines contain the specific genes of the germ which are translated into specific protein in the vaccinated person’ body (such as mRNA vaccines).

Covid-19 Vaccine

The novel Coronavirus is called covid-19. It has spread across the continents causing huge number of infections and significant number of deaths worldwide.
To control the spread and protect the population across the world, many different types of Covid-19 vaccines have been developed and used in many countries. It is important for all covid-19 vaccine candidates to discuss their medical condition with the attending doctor at the vaccine center (read: Pre-Covid-19 vaccination guide for public). 
Our body produces immune response or antibodies when exposed to the whole germ or a small piece (antigen) of the germ. All Covid-19 vaccines developed so far are targeting covid-19 virus spike protein as a main antigen against which antibodies are generated.

There are 4 main types of Covid-19 vaccines that are currently in use worldwide:

Whole Virus (Inactivated Covid-19 virus) Vaccine Protein subunit or purified protein-based Vaccine
This type of vaccine uses old conventional well-established technology of vaccine manufacturing. There are many childhood vaccines in use for many decades that are developed using this technology platform.
In this type of vaccine, viruses are inactivated using strong chemicals and physical conditions (temperature, pH) so that the genetic material of the virus is destroyed making it unable to cause infection. However, the virus can still stimulate the immune system to produce antibodies and immune cells for protection.
Sinopharm (Chinese company) Covid-19 vaccine is manufactured using inactivated virus technology
Protein sub-unit vaccines uses the protein or a small part of a protein of the germ. The target protein can be made and purified from the germ (such as spike protein in coronavirus) in the labs and manufacturing facilities. The purified protein of the germ is used in the vaccine as an antigen to activate the immune system to produce antibodies and thus provides protection against infection.
Many vaccines are made using this established technology platform such as Hepatitis B vaccine.
Novavax (an American company) is close to launch coronavirus vaccine using this technology
Viral Vector (Adenovirus based Vaccine) Nucleic Acid (mRNA-based Vaccine)
In this type of coronavirus vaccine, a harmless adenovirus shell is used in which coronavirus spike protein gene is added to transport the gene to vaccine recipient body. The objective is that the gene can made the spike protein in the vaccine recipient body triggering the immune system to produce antibodies against the spike protein.
This is a new vaccine manufacturing technology platform and there is only one vaccine earlier developed using this technology. The long term effects of the vaccines are unknown at this point.
AstraZeneca and Russian vaccines are developed using this technology
In this type, the gene (mRNA) that encodes coronavirus spike protein is directly given as a vaccine. The spike protein mRNA is processed to prevent degradation in the body. The mRNA produces the spike protein in our body. The spike protein the triggers the immune system to produce antibodies to protect from covid-19 infection.
This is also a new technology and approach to manufacture vaccines. No vaccines or any other drug is developed using this technology. The long term effects of the vaccines are unknown at this point.
Pfizer/ BioNTech and Moderna have used mRNA technology for their covid-19 vaccines

The race for a COVID-19 vaccine assets

Can vaccine cause side effects?

Like all other medicines, vaccines may also cause some side effects or adverse reactions, however they are very rare. Vaccines that are in use for decades and have long safety profile are considered much safer.
As per recommendation, after all vaccinations, it is important to stay in clinic or hospital for 30 minutes after the administration of the vaccine to ensure availability of medical support in case of an acute side effect or allergic reaction that is very rare to occur. Vaccine side effects are usually non-serious and short-lived.

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