"For somebody who's already been fully vaccinated, they can wear the mask out of solidarity or in a symbolic sense, but their wearing a mask indoors is not benefiting anyone else," explained Vinay Prasad, an epidemiologist and biostatistician at the University of California, San Francisco (UCSF). "Masking is a tool, and vaccines are the solution," said Gandhi, who has written seven papers on the importance of masking to stem the pandemic, and was one of the earliest proponents of universal masking in the United States. There is another good reason to ease restrictions, and that is to motivate people who are hesitant to roll up their sleeves, said Angela Rasmussen, of the Vaccine and Infectious Disease Organization in Canada. This is becoming more important as the rate of vaccination in the United States has fallen from its early April peak and supply is outstripping demand in many regions. But she added it will be important to define clear metrics, "because one of the biggest problems with communication during the pandemic has been the perception that public health agencies are moving the goalposts."