This is a bittersweet moment in the global fight against the Covid pandemic. Joy that at least two vaccine trials have produced extremely promising results is tempered by the continued spread of the disease across much of the world. To put it bluntly, the global containment effort has had limited success. Stephen Sackur speaks to Dr David Nabarro, the World Health Organisation’s special envoy for Covid-19. Are countries doing enough to minimise the damage done before mass vaccination changes the game?