Abstract:
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a new
beta coronavirus that emerged at the end of 2019 in the Hubei province of China.
SARS-CoV-2 causes coronavirus disease 2019 (COVID-19) and was declared a
pandemic by the World Health Organization (WHO) on 11 March 2020. Herd or
community immunity has been proposed as a strategy to protect the vulnerable, and
can be established through immunity from past infection or vaccination. Whether SARSCoV-2 infection results in the development of a reservoir of resilient memory cells is under
investigation. Vaccines have been developed at an unprecedented rate and 7 408 870
760 vaccine doses have been administered worldwide. Recently emerged SARS-CoV-2
variants are more transmissible with a reduced sensitivity to immune mechanisms. This is
due to the presence of amino acid substitutions in the spike protein, which confer a
selective advantage. The emergence of variants therefore poses a risk for vaccine
effectiveness and long-term immunity, and it is crucial therefore to determine the
effectiveness of vaccines against currently circulating variants. Here we review both
SARS-CoV-2-induced host immune activation and vaccine-induced immune
responses, highlighting the responses of immune memory cells that are key indicators
of host immunity. We further discuss how variants emerge and the currently circulating
variants of concern (VOC), with particular focus on implications for vaccine effectiveness.
Finally, we describe new antibody treatments and future vaccine approaches that will be
important as we navigate through the COVID-19 pandemic.
