Covid-19 vaccines and variants of concern: A review.

Abstract

Since the outbreak of coronavirus disease 2019 (Covid‐19) in December 2019, caused by the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), the number of confirmed infections has risen to more than 242 million worldwide, with nearly 5 million deaths. Currently, nine Covid‐19 vaccine candidates based on the original Wuhan‐Hu‐1 strain are at the forefront of vaccine research. All nine had an efficacy over 50% against symptomatic Covid‐19 disease: NVX‐CoV2373 (∼96%), BNT162b2 (∼95%), mRNA‐1273 (∼94%), Sputnik V (∼92%), AZD1222 (∼81%), BBIBP‐CorV (∼79%), Covaxin (∼78%), Ad26.CoV.S (∼66%) and CoronaVac (∼51%). However, vaccine efficacy (VE) can be jeopardised by the rapid emergence and spread of SARS‐CoV‐2 variants of concern (VOCs) that could escape from neutralising antibodies and/or cell‐mediated immunity. Rare adverse events have also been reported soon after administration of viral vector and mRNA vaccines. Although many Covid‐19 vaccines have been developed, additional effective vaccines are still needed to meet the global demand. Promising Covid‐19 vaccines such as WIBP‐CorV, AD5‐nCOV, ZyCoV‐D, CVnCoV, EpiVacCorona and ZF2001 have advanced to clinical studies. This review describes the most relevant mutations in the SARS‐CoV‐2 spike protein, discusses VE against VOCs, presents rare adverse events after Covid‐19 vaccination and introduces some promising Covid‐19 vaccine candidates.