SARS-CoV-2 originated in Wuhan, Hubei province of China and was declared as a pandemic by WHO in March 2020. It has not been the first time this world has been hit by a lethal pandemic. Spanish Flu prevailed a century back whereas SARS-CoV-1 and MERS like viruses have also ensnared in the form of epidemics. Such lethal viruses establish themselves in the human population by aquiring the mutations and resultantly enhance their pathogenicity. Up till now many variants of SARS-CoV-2 has been reported, one of the biggest reasons is the briskly aquiring mutations rate as it is a single stranded RNA virus that lacks proof reading ability. Currently, delta variant is spreading with the greatest mortality rate. Ever since China has released the genomic sequence of SARS-CoV-2 online, researchers from all over the world have joined hands to come up with a vaccine. More than 90 vaccines have underway but only a few have been approved by FDA for administration into human beings. Emergency Use Authorization has been granted to a lot of vaccines and Pfizer is the first mRNA vaccine to have succeeded all the trials with an efficacy of more than 90 % against Covid-19. In this review, short briefing is provided related to all the important vaccines worldwide while a detailed review of PfizerNBiotech has been given to highlight the prospects of a vaccine which is new in its kind.

Keywords : Covid-19; Vaccines; PfizerBioNtech; immune responses; Doses; Efficacy; Variants; mRNA based vaccines; clinical trials