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November 24 2020 at 05:12 PM by Samikshya Joshi



A vaccine is a substance that helps protect against certain diseases. Vaccines contain a dead or weakened version of a microbe. It helps your immune system recognize and destroy the living microbe during a future infection. It is a safe, and effective way of protecting people against harmful diseases before they come into contact with them. Vaccines train your immune system to create antibodies, just as it does when it’s exposed to a disease. Most vaccines are given by an injection, but some are given orally (by mouth) or sprayed into the nose. Vaccines reduce risks of getting a disease by working with your body’s natural defenses to build protection.

When you get a vaccine, your immune system responds. It:

·    Recognizes the invading germ, such as the virus or bacteria.


·    Produces antibodies. Antibodies are proteins produced naturally by the immune system to fight disease.


·    Remembers the disease and how to fight it. If you are then exposed to the germ in the future, your immune system can quickly destroy it before you become unwell.

The vaccine is therefore a safe and clever way to produce an immune response in the body, without causing illness.

Our immune systems are designed to remember. Once exposed to one or more doses of a vaccine, we typically remain protected against a disease for years, decades or even a lifetime. This is what makes vaccines so effective. Rather than treating a disease after it occurs, vaccines prevent us in the first instance from getting sick.

1.  Who should get vaccinated?

Nearly everyone can get vaccinated. However, because of some medical conditions, some people should not get certain vaccines, or should wait before getting them. These conditions can include:

·    Chronic illnesses or treatments (like chemotherapy) that affect the immune system;

·    Severe and life-threatening allergies to vaccine ingredients, which are very rare;

·    If you have severe illness and a high fever on the day of vaccination.


2.   What types of COVID-19 vaccines are being developed? How would they work?

Scientists around the world are developing many potential vaccines for COVID-19. These vaccines are all designed to teach the body’s immune system to safely recognize and block the virus that causes COVID-19. Several different types of potential vaccines for COVID-19 are in development, including:

·    Inactivated or weakened virus vaccines, which use a form of the virus that has been inactivated or weakened so it doesn’t cause disease, but still generates an immune response.


·    Protein-based vaccines, which use harmless fragments of proteins or protein shells that mimic the COVID-19 virus to safely generate an immune response.


·    Viral vector vaccines, which use a virus that has been genetically engineered so that it can’t cause disease, but produces coronavirus proteins to safely generate an immune response.


·    RNA and DNA vaccines, a cutting-edge approach that uses genetically engineered RNA or DNA to generate a protein that itself safely prompts an immune response.


3.   Various types of Covid-19 vaccines being prepared:


A.  Sputnik V - formerly known as Gam-COVID-Vac and is developed by the Gamaleya Research Institute in Moscow – was approved by the Ministry of Health of the Russian Federation on 11 August. It an adenoviral-based vaccine against the SARS-CoV-2 coronavirus. Sputnik V uses a weakened virus to deliver small parts of a pathogen and stimulate an immune response. The Sputnik V vaccine was developed by the same government labs that developed what is claimed “an effective against the Ebola virus, as well as a vaccine against the MERS virus. Based on the analysis, the efficiency of Sputnik V was 95%. It can be stored at a normal fridge temperature of 2-8 degrees centigrade


B.  EpiVacCorona- A second vaccine from Russia is also in Phase 3 clinical trials. EpiVacCorona vaccine is based on peptide antigens for the prevention of COVID-19. It contains a part of a macromolecule of the SARS-CoV-2 antigen, recognized by the immune system.


C.  Moderna’s mRNA-1273- It is an mRNA vaccine against COVID-19 encoding for a prefusion stabilized form of the Spike (S) protein, which was co-developed by Moderna and investigators from NIAID’s Vaccine Research Center. 


D.  University of Oxford and AstraZeneca’s AZD1222- The vaccine can be stored, transported and handled at normal refrigerated conditions (2-8 degrees Celsius/ 36-46 degrees Fahrenheit) for at least six months and administered within existing healthcare settings. It uses a replication-deficient chimpanzee viral vector based on a weakened version of a common cold virus (adenovirus) that causes infections in chimpanzees and contains the genetic material of the SARS-CoV-2 virus spike protein


E.  Pfizer and BioNTech's BNT162: The BNT162 program is evaluating at least 4 experimental vaccines, each of which represents a unique combination of messenger RNA (mRNA) format and target antigen. Two of the 4 vaccine candidates include a nucleoside modified mRNA (modRNA), one includes uridine containing mRNA (uRNA), and the fourth vaccine candidate utilizes self-amplifying mRNA (saRNA). Each mRNA format is combined with a lipid nanoparticle (LNP) formulation. BNT162b1 and BNT162b2 are both nucleoside-modified RNAs, formulated in lipid nanoparticles. BNT162b1 encodes an optimized SARS-CoV-2 receptor-binding domain (RBD) antigen, while BNT162b2 encodes an optimized SARS-CoV-2 full-length spike protein antigen. The larger spike sequence is included in two of the vaccine candidates, and the smaller optimized RBD from the spike protein is included in the other 2 vaccine candidates. The RBD-based candidates contain the piece of the spike that is thought to be most important for eliciting antibodies that can inactivate the virus.


F.  Covaxin: It is the most advanced Indian experimental vaccine. Bharat Biotech announced that it had developed a vaccine against the novel coronavirus, named Covaxin, together with the Indian Council of Medical Research (ICMR) and the National Institute of Virology (NIV), Pune. It has currently invested in two other vaccines: CoroFlu in collaboration with FluGen Inc. and the University of Wisconsin-Madison, and an inactivated rabies vaccine vehicle for coronavirus proteins. Covaxin is 50- 60 percent effective.


  However, although so many vaccines are being prepared for COVID-19, the storing temperature is the most important criteria.



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