Immunization is one of the most cost-effective public health interventions to date, saving an estimated 2 to 3 million lives each year. As a direct result of immunization, the world is closer than ever to eradicating polio, and deaths from measles – a major child killer – have declined by 73 per cent worldwide between 2000 and 2018, saving an estimated 23.2 million children’s lives. The emergence of COVID-19, however, threatens to reverse this progress by severely limiting access to life-saving vaccines.