New York Comic Con is set to return for a reduced capacity 2021 edition on October 7-10 at Javits Center. The convention already said they would be requiring that face coverings be worn by all attendees, including exhibitors and staff, and they've now issued a health and safety update with additional COVID policies. They'll require all ticketholders 12 years old and older to provide proof of vaccination to attend; children under the age of 12 will be able to provide a negative PCR or antigen COVID test result instead.
As for face coverings, they'll be required to be worn by all attendees, including "cosplayers, exhibitors, guests, artists, and staff." They continue, "headwear and cosplay pieces which cover the face in a manner which does not visibly fit the face covering requirements will not be permitted," including costume masks. Find face covering guidelines here.