Systematic Review of the SARS-CoV-2 Viral Vector Vaccine AstraZeneca (Azd1222)

Abstract

It has been more than two years since the spread of the COVID-19 pandemic all over the world. Scientists still are in search of a permanent treatment and cure of this infectious disease. In this regard, on 20th April, 2020, AstraZeneca in collaboration with the Oxford University came up with a recombinant adenovirus-based vaccine labeled as “ChAdOx1 nCoV-19” or “AZD1222”. Approximately, 22 viral vector-based vaccines are in the trial stage and ChAdOx1 nCoV-19 falls under the category of non-replicating viral vector-based vaccines. During vaccine development, ChAdOx-1 vector was specifically designed by red lambda recombination of Y25 serotype (chimpanzee) with HAdV-C5 serotype (human). In July 2020, clinical trials were initiated but due to some controversial side effects, these trials were halted for a while and resumed later on. AstraZeneca has been reported to generate both humoral and cell mediated immune responses. This vaccine exhibited 63% efficacy with few side effects. It also exhibited dwindling efficacy against the emerging variants of COVID-19. Since then, heterologous prime boost vaccination has been initiated, exhibiting elevated efficacy. Until now, 42.6% population of the world has been vaccinated with a single dose and this number is rising rapidly. However, due to the emerging variants of COVID-19, the efficacy of the majority of vaccines is decreasing. So, the manufacturers must work on making the vaccines more effective against these new variants as well. This review is written with the intention of summing up all the reported data regarding AZD1222 in order to provide a proper overview.