(Reuters) - Fully vaccinated people can safely engage in outdoor activities like walking and hiking without wearing masks but should continue to use face-coverings in public spaces where they are required, U.S. health regulators said on Tuesday. The updated health advice comes as more than half of all adults in the United States have now received at least one dose of COVID-19 vaccine, according to the U.S. Centers for Disease Control and Prevention (CDC). "The release of these new guidelines is a first step at helping fully vaccinated Americans resume activities they had stopped doing because of the pandemic, while...