Monica Aparecida Calazans, 54, a nurse, a volunteer in COVID-19 vaccine trial for Sinovac, poses for a photograph in Sao Paulo, Brazil, December 10, 2020. Calazans who has one son, said: "My brother, who is 47 years old had COVID-19, had a severe form of the disease. We even thought we would lose him. And then I thought, 'If I don't take the vaccine, we will never know if it works or not.' For him, but for everyone else too, I had the drive to take part in the trial." Picture taken with a slow shutter speed. REUTERS/Amanda Perobelli SEARCH "PEROBELLI VACCINE" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES