Challenges in creating herd immunity to SARS-CoV-2 infection by mass vaccination

Abstract

Vaccines to protect against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have risen up the agenda of most policy makers and individuals as the second wave of COVID-19 in northern hemisphere countries grows and there is increasing pressure on health-care systems. For any licensed vaccine, efficacy and duration of protection are key issues. Vaccine efficacies to protect against infection above 80% are desirable,1 but duration of protection will remain uncertain for a number of years post licensure of COVID-19 vaccines.