The socioeconomic burden of COVID-19 and pressure on health-care systems can only be reduced by achieving herd immunity against SARS-CoV-2. For herd immunity to be achieved, it has been estimated that, depending on the efficacy of the vaccines employed, approximately 60–100% of the global population needs to be vaccinated.1Anderson RM Vegvari C Truscott J Collyer BS Challenges in creating herd immunity to SARS-CoV-2 infection by mass vaccination.