EVALUATION OF ADENOVIRAL VECTOR-BASED VACCINES FOR PREVENTION OF COVID-19 – AN OVERVIEW

ABSTRACT

The novel coronavirus and its emerging variants have continued to affect 50.4 million people worldwide, increasing the need for safe and effective vaccines. According to the World Health Organization guidelines, the efficacy of a vaccine should be at least 30% in all age groups and protect for a longer duration without any life-threatening adverse effects. At present, there are 319 vaccines in various stages of development, of which 16 are authorized for emergency use. Of these 16 vaccines, five vaccines are based on adenoviral vectors. This review is focused on understanding the safety and efficacy of the approved adenoviral vector vaccines for COVID-19, particularly highlighting the interim analysis of phase 3 clinical trials of AZD1222, Gam-Covid-Vac, Ad26.COV2.S, and AD5-nCOV vaccine. The efficacy of AZD1222, Gam-Covid-Vac, Ad26.COV2.S, and AD5-nCOV vaccine were found to be 70.4%, 95%, 66%, and 65.7%, respectively. Some serious adverse events such as deep vein thrombosis and thrombosis with thrombocytopenia syndrome were observed among AZD1222 and Ad26.COV2.S vaccinated individuals. Meanwhile, Gam-Covid-Vac and AD5-nCOV vaccines did not report any significant adverse events. In addition, we have also focused on the efficacy of these vaccines against SARS-CoV-2 variants such as B.1.1.7, B.1.351, and P.1. Although the efficacy of these approved vaccines against novel SARS-CoV-2 variants, pediatric and geriatric population and long-term efficacy remains uncertain, they are reasonably efficient in preventing mortality due to COVID-19.