(Reuters) - 1/VACCINE RACEU.S. President Donald Trump has put his faith in anti-malarial drug hydroxychloroquine to ward off COVID-19, but governments and investors are focusing on a vaccine. Without one, it's unlikely economic activity can resume fully.So the race is on, and the rewards are rich: AstraZeneca has vaulted into the position of the most valuable British company after receiving a U.S. pledge for up to $1.2 billion for its experimental vaccine.Pharma/biotech shares have outperformed..