Ana Marcela Rojas Fonseca Hial, 49, a doctor, a volunteer in COVID-19 vaccine trial for AstraZeneca, poses for a photograph in Sao Paulo, Brazil, December 10, 2020. Hial who has one son said: "The hardest thing in the pandemic has been seeing whole families sick and the sense of powerlessness that you can't resolve the situation … This global push to resolve the situation is a very special moment." Picture taken with a slow shutter speed. REUTERS/Amanda Perobelli SEARCH "PEROBELLI VACCINE" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES