What do we know about blood clots and the AstraZeneca Covid vaccine?

The rollout of the Oxford-AstraZeneca Covid vaccine hasn’t been straightforward. After weathering early questions about its efficacy, there has been a series of rare blood clotting incidents, resulting in several deaths overseas. As authorities investigate whether the vaccine is responsible, some countries have paused their programs while others, such as the UK and Australia, are forging ahead. Medical editor Melissa Davey explores what we know about the risks and benefits