A focused review on technologies, mechanisms, safety, and efficacy of available COVID-19 vaccines

>20 months has been passed since the detection of the first cases of SARS-CoV-2 infection named COVID-19 from Wuhan city of China. This novel coronavirus spread rapidly around the world and became a pandemic. Although different therapeutic options have been considered and approved for the management of COVID-19 infection in different stages of the disease, challenges in pharmacotherapy especially in patients with moderate to severe COVID-19 and with underlying diseases have still remained. Prevention of infection through public vaccination would be the only efficient strategy to control the morbidity and mortality caused by COVID-19. To date, several COVID-19 vaccines using different platforms including nucleic acid-based vaccines, adenovirus-based vaccines, protein-based vaccines, and inactivated vaccines have been introduced among which many have received approval for prevention against COVID-19. In this comprehensive review, available COVID-19 vaccines have been discussed. The mechanisms, safety, efficacy, dosage, dosing intervals, possible adverse reactions, storage, and coverage of these four different vaccine platforms against SARS-CoV-2 variants have been discussed in detail and summarized in tabular format for ease of comparison and conclusion. Although each COVID-19 vaccine has various advantages and disadvantages over the others, accessibility and affordability of approved vaccines by the official health organizations, especially in developing countries, would be essential to terminate this pandemic. The main limitation of this study was the lack of access to the clinical data on available COVID-19 vaccines developed in Eastern countries since the data on their efficacy, safety, and adverse reactions were limited.