Nurse Sodkhuu Galbadrakh clutches a box of Covid-19 vaccines on his lap as he journeys along a bumpy track through a remote region of the Mongolian steppe, going home to home to offer booster doses to herders. The country of three million has taken some of the world's toughest and most enduring measures against the coronavirus pandemic, shutting schools for much of the last two years and closing borders. Its vaccination programme has seen huge take-up with more than 90 percent of adults receiving two jabs. But the booster programme is seeing patchier success among nomadic communities thanks to both online misinformation and the sheer logistical challenge that comes with reaching remote communities in such a vast nation. Mongolia is one of the most sparsely populated countries in the world and about one-third of the population are nomadic.