Abstract
BACKGROUND: The SARS-CoV-2 coronavirus epidemic is hastening the discovery of the most efficient vaccines. The development of cost-effective vaccines seems to be the only solution to terminate this pandemic. However, the vaccines' effectiveness has been questioned due to recurrent mutations in the SARS-CoV-2 genome. Most of the mutations are associated with the spike protein, a vital target for several marketed vaccines. Many countries were highly affected by the 2nd wave of the SARS-CoV-2, like the UK, India, Brazil and France. Experts are also alarming the further COVID-19 wave with the emergence of Omicron, which is highly affecting the South African populations. This review encompasses the detailed description of all vaccine candidates and COVID-19 mutants that will add value to design further studies to combat the COVID-19 pandemic. METHODS: The information was generated using various search engines like google scholar, PubMed, clinicaltrial.gov.in, WHO database, ScienceDirect, and news portals by using keywords SARS-CoV-2 mutants, COVID-19 vaccines, efficacy of SARS-CoV-2 vaccines, COVID-19 waves. RESULTS: This review has highlighted the evolution of SARS-CoV-2 variants and the vaccine efficacy. Currently, various vaccine candidates are undergoing several phases of development. Their efficacy still needs to check for newly emerged variants. We have focused on the evolution, multiple mutants, waves of the SARS-CoV-2, and different marketed vaccines undergoing various clinical trials and the design of the trials to determine vaccine efficacy. CONCLUSION: Various mutants of SARS-CoV-2 arrived, mainly concerned with the spike protein, a key component to design the vaccine candidates. Various vaccines are undergoing clinical trial and show impressive results, but their efficacy still needs to be checked in different SARS-CoV-2 mutants. We discussed all mutants of SARS-CoV-2 and the vaccine's efficacy against them. The safety concern of these vaccines is also discussed. It is important to understand how coronavirus gets mutated to design better new vaccines, providing long-term protection and neutralizing broad mutant variants. A proper study approach also needs to be considered while designing the vaccine efficacy trials, which further improved the study outcomes. Taking preventive measures to protect from the virus is also equally important, like vaccine development.