COVID-19 vaccines: concerns beyond protective efficacy and safety.

Lai, Chih-Cheng; Chen, I-Tzu; Chao, Chien-Ming; Lee, Ping-Ing; Ko, Wen-Chien; Hsueh, Po-Ren

INTRODUCTION Several vaccine candidates have been developed using different platforms, including nucleic acids (DNA and RNA), viral vectors (replicating and non-replicating), virus-like particles, peptide-based, recombinant proteins, live attenuated, and inactivated virus modalities. Although many of these vaccines are undergoing pre-clinical trials, several large clinical trials investigating the clinical efficacy and safety of coronavirus disease 2019 (COVID-19) vaccines have produced promising findings. AREAS COVERED In this review, we provide a status update on COVID-19 vaccines currently undergoing clinical trials and discuss issues of concern beyond vaccine efficacy and safety, including dosing regimens, the mixed vaccine strategy, prior severe acute respiratory syndrome coronavirus-2 infection, antibody levels, cellular immunity and protection, variants of concern, COVID-19 vaccine distribution, vaccination willingness, herd immunity, immunity passports, and vaccine indications. EXPERT OPINION Four vaccines have obtained emergency use authorization, 87 are at the clinical development stage, and 186 are in pre-clinical development. While the knowledge and development of COVID-19 vaccines is rapidly expanding, the benefits of COVID-19 vaccines must outweigh the potential risks of adverse events. To combat the COVID-19 pandemic, clinicians should consistently update COVID-19-associated information, and healthcare authorities and manufacturers should work together to provide adequate and appropriate vaccinations for the prevention of COVID-19.