he spread of SARS-CoV-2, the causative agent of COVID-19, has resulted in an unprecedented global public health and economic crisis 1,2. The outbreak was declared a pandemic by the World Health Organization on 11 March 2020 3 , and development of COVID-19 vaccines has been a major undertaking in fighting the disease. As of December 2020, many candidate vaccines have been shown to be safe and effective at generating an immune response 4-6 , with interim analysis of phase III trials suggesting efficacies as high as 95% 7-9. At least two vaccine candidates have been authorized for emergency use in the USA 10,11 , the UK 12,13 , the European Union 14 and elsewhere, with more candidates expected to follow soon. For these COVID-19 vaccines to be successful, they need to be not only be proven safe and efficacious, but also widely accepted. It is estimated that a novel COVID-19 vaccine will need to be accepted by at least 55% of the population to provide herd immunity, with estimates reaching as high as 85% depending on country and infection rate 15,16. Reaching these required vaccination levels should not be assumed given well-documented evidence of vaccine hesitancy across the world 17 , which is often fuelled by online and offline misinformation surrounding the importance, safety or effectiveness of vaccines 18-20. There has been widely circulating false information about the pandemic on social media platforms, such as that 5G mobile networks are linked with the virus, that vaccine trial participants have died after taking a candidate COVID-19 vaccine, and that the pandemic is a conspiracy or a bioweapon 21-23. Such information can build on pre-existing fears, seeding doubt and cynicism over new vaccines, and threatens to limit public uptake of COVID-19 vaccines. While large-scale vaccine rejection threatens herd immunity goals, large-scale acceptance with local vaccine rejection can also have negative consequences for community (herd) immunity, as clustering of non-vaccinators can disproportionately increase the needed percentage of vaccination coverage to achieve herd immunity in adjacent geographical regions and encourage epidemic spread 24. Estimates of acceptance of a COVID-19 vaccine in June 2020 suggest that 38% of the public surveyed in the UK and 34.2% of the public in the USA would accept a COVID-19 vaccine (a further 31% and 25% were, respectively, unsure that they would accept vaccination against COVID-19) 25. Worryingly, more recent polling in the USA (September 2020) has shown significant falls in willingness to accept a COVID-19 among both males and females, all age groups, all ethnicities and all major political groups 26 , possibly due to the heavy politicization of COVID-19 vaccination in the run up to the 2020 presidential election on both sides of the political debate 27,28. The public's willingness to accept a vaccine is therefore not static; it is highly responsive to current information and sentiment around a COVID-19 vaccine, as well as the state of the epidemic and perceived risk of contractin...