Next-generation COVID-19 vaccines: Opportunities for vaccine development and challenges in tackling COVID-19

The ongoing COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become a global threat. Although non-pharmaceutical interventions have been rigorously and widely implemented, living conditions caused by the pandemic will last until highly effective vaccines are successfully improved and globally administered. Several first-generation COVID-19 vaccines were approved at the end of 2020. However, the COVID-19 pandemic is persisting worldwide. To be clear, the efficiency and the coverage of current vaccines are insufficient, but newly emerging and rapidly spreading variants are the most pressing concern. A second-generation COVID-19 vaccine worth mentioning, NVX-CoV2373, has demonstrated 90% overall efficacy as well as a high level of efficacy against circulating variants in Phase 3 clinical trials. Currently, NVX-CoV2373 is the only vaccine that has proven successful against variants during Phase 3/4 trials. Therefore, developing the next generation of vaccines is a promising strategy to ultimately prevail against SARS-CoV-2. This review provides up-to-date information on COVID-19 vaccines in terms of their efficacy and new platforms and the progression of COVID-19 vaccination. Moreover, this review also summarizes the efficacy of approved COVID-19 vaccines against variants. Lastly, this review highlights the global challenges for COVID-19 vaccines in development and vaccination, and it discusses opportunities for development of future COVID-19 vaccines and vaccination coverage.