The Journey of Candidate vaccines for COVID-19

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Duleep Tyagi 

Vaccines are meant for controlling the spread of infectious diseases which generally composed of attenuated or inactivated pathogens and can elicit a defensive immune response. For example, in the past major vaccination drives have successfully eradicated smallpox and reduced other infectious diseases such as polio, measles, and diphtheria. In recent years, thanks to the next-generation vaccine delivery technology and advances in biotechnology that have improved the production of recombinant proteins.

The general stages for developing a vaccine typically include the following: • Exploratory stage • Pre-clinical stage • Clinical development • Regulatory review and approval • Manufacturing • Quality control

To pass through all the stages and get the approval, the development of a vaccine may take several years. However, the genetic sequence of SARS-CoV-2 has paved a way for many companies for the extensive development programs of vaccines worldwide. On March 16, 2020, the first COVID-19 vaccine candidate entered human clinical trials. The global COVID-19 vaccine candidates as of now have reached 115, of which 73 are at preclinical stages. Among which mRNA-1273 from Moderna, Ad5-nCoV from CanSino Biologicals, INO-4800 from Inovio, LV-SMENP-DC and pathogen-specific aAPC from Shenzhen Geno-Immune Medical Institute entered into the clinical development stage. The clinical development stage is divided into three phases:

Phase I

The trial vaccine is tested upon a small group of people.

Phase II

Given to people for whom it is intended

Phase III

Tested upon several thousands of people for efficacy and safety. And several vaccines undergo Phase IV too.

Further, to improve vaccine elicitation of cell-mediated and mucosal immunity, a wide range of technology platforms are being used for the development of vaccines against COVID-19. These include DNA-based, viral vector-based, recombinant protein, live attenuated virus and inactivated virus approaches. Amazingly, some of these platforms that are being used for the development of vaccines for COVID-1, are not used for licensed vaccines.

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