Vaccines for COVID 19

Overview

The overarching goal is for COVID-19 vaccines to contribute significantly to the equitable protection and promotion of human well-being among people globally. The vaccine is to be used in conjunction with other control measures. In the longer term, the vaccine is intended to be used for active immunization of people at-risk to prevent COVID-19.

Scientists throughout the world have accelerated the process to develop safe and effective COVID-19 vaccines. Vaccines aim to expose the body to an antigen and provoke an immune response that can block or kill the virus if a person becomes subsequently infected, without causing the disease.

Globally, over 274 candidate vaccines are in different stages of development as of 4 December 2020.  The majority of vaccines in clinical evaluation as of 4 December 2020 will require a twodose schedule to be administered two, three or four weeks apart, and is need to be administered through the intramuscular route.

Scientific techniques used

As part of the global efforts for rapid development of a safe and effective COVID-19 vaccine, various scientific techniques like the use of different viruses or viral parts are being developed. The COVID-19 vaccines under development use one of the following techniques:

• Virus Vaccine
• Viral vector vaccine
• Nucleic acid vaccines
• Protein based vaccine

Virus vaccines

These vaccines use the virus itself in a weakened or inactivated form. Vaccines against measles and polio (oral) are made in this manner. There are two types of virus vaccines under development against coronavirus, weakened virus and inactivated virus vaccines.

Viral-vector vaccines

In the development of these vaccines, a virus (such as adenovirus or measles), is genetically engineered to produce coronavirus proteins in the body, but the virus is weakened and cannot cause disease. The two types of viral-vector vaccines under development are replicating viral vector (can replicate within cells) and non-replicating viral vector (cannot replicate within cells).

Nucleic-acid vaccines

In these vaccines, nucleic acid (DNA or RNA) is inserted into human cells. These human cells then produce copies of the virus protein which produces an immune response. The two types of nucleic-acid vaccines under development are DNA vaccine and RNA vaccine.

Protein-based vaccines

These vaccines use virus protein fragments or protein shells which are injected directly into the body. The two types of protein-based vaccines being developed against the coronavirus are the protein subunit vaccines and virus-like particle vaccines.

Development of COVID 19 vaccine

The Development of a vaccine is a time-consuming process that includes the following phases:

• Pre-clinical : Vaccine development in laboratory
• Phase 1 : Clinical trial (8-10 participants) : For testing vaccine safety
• Phase 2 : Clinical trial (50-100 participants) : For testing vaccine immunogenicity i.e. production of antibodies against virus
• Phase 3 : Clinical trial (30,000-50,000 participants) : For testing actual protection offered by the vaccine

The vaccine development process has been fast-tracked and multiple platforms are under development. Among those with the greatest potential for speed are DNA and RNA-based platforms, followed by those for developing recombinant-subunit vaccines. RNA and DNA vaccines can be made quickly because they require no culture or fermentation, instead use synthetic processes

Source : Operational guidelines of COVID-19 vaccines