NITA BHALLA and MOHAMMED OMER SOMALI cattle herder Omar Hussein isn't joining the global scramble for a COVID-19 vaccine - he's not sure the jab will even reach his besieged town in southwestern Somalia. The 28-year-old, who has spent much of his life living in a volatile region infiltrated by al Qaeda-linked Islamist insurgents, has bigger problems on his mind. "I know COVID-19 is a killer, everyone knows that. It killed many in Western countries, but not here thanks to God," the father of three told the Thomson Reuters Foundation by phone from his home in Bulo Fulay town in…