With more than 1bn coronavirus vaccine doses administered to adults around the world, debate is turning to the contentious question of whether or when to extend vaccinations to children.

The biggest vaccine manufacturers have all trialled their jabs on young people, including babies in some cases. Canada this week become the first country to approve a vaccine for children as it authorised the BioNTech/Pfizer shot, which the company said was 100 per cent effective in adolescents, for those aged 12-15.

Yet a series of interlinked questions over the ethics of giving out Covid-19 vaccines to children have sparked intense debate with no simple answers. How governments respond will be a crucial factor in shaping who receives the next 1bn vaccine doses.