 With almost 8 billion people on Earth, it will take a while to make enough vaccine doses for everyone. So governments will need to decide which groups to prioritize to receive the doses first, in each country and across the world. Let's imagine there are nine people in your family. But you can only give three doses of a vaccine now. You'll get three more in six months time and the final three next year. You have to decide who gets the vaccine first. You may choose to give it to your grandparents because they would be most at risk of dying from COVID-19. What if you had a sibling with asthma? Would they be first? Maybe you'd prioritize those working who regularly come into contact with people outside the house. There's no perfect answer. Research shows that to reduce strain on our health services and reduce restrictions on other parts of society, we should give it to the most vulnerable people first. Not just in wealthier countries that have purchased the most vaccine doses. The World Health Organization have a recommended priority order and most countries are basing their response on this. The good news is, multiple vaccines are proving safe and effective, making it much more likely that people around the world who need a vaccine will be able to receive one, helping reduce the impact of COVID-19 on societies across the globe.