AP Health and Science journalists Christina Larson and Angie Wang teamed up with Brazil-based journalists Lucas Dumphreys and Bruna Prado to report exclusively on a pathbreaking campaign to vaccinate an endangered species of monkey in the wild – an unconventional approach that may prevent extinction, but also raises questions about how far to intervene to protect wildlife. The story started when science writer Christina Larson heard from a source about endangered golden lion tamarins dying from an outbreak of yellow fever in Brazil. Larson kept in touch with scientists in Brazil for more than two years eventually secure permission for a team of AP journalists to follow their efforts on the ground in the rainforest. Larson and Health & Science videojournalist Angie Wang, together with Rio-based videojournalist Lucas Dumphreys and photographer Bruna Prado, dusted themselves in mosquito-repellant and schlepped up steep, muddy hillsides in Brazil’s Atlantic Forest to follow as biologist Andreia Martins released newly vaccinated tamarins back into the wild.