The United States Food and Drug Administration has given emergency use authorisation to the Pfizer coronavirus vaccine candidate. US authorisation comes weeks after UK became the first nation in the world to begin mass rollout of the vaccine against Covid-19. The Pfizer vaccine has been approved for the public in the UK, Canada, Bahrain and Saudi Arabia. Earlier this week, the United Kingdom became the first country in the world to administer the new coronavirus vaccine developed jointly by the American drugmaker Pfizer and Germany's BioNTech in an inoculation programme watched closely around the world. However, the US needs to vaccinate close to 70 per cent of the population to achieve herd immunity, and it's going to take time, even if the vaccine is widely accepted.