Andrea Silva Borda Nascimento had her three children vaccinated as part of the dengue vaccine trial. “We have a family history. I had dengue, and my son Zika. In our apartment block, out of four families and a total of 18 people, eight had dengue. As the vaccine has already been tested for years, I was confident it could be good,” she says. “But people are very scared of dying from the vaccine or it having any side-effect.”

Photograph: Adrienne Surprenant/Collectif © Wellcome