A look back at lockdowns, vaccines and variants defining the Covid-19 pandemic in 2021

As the Covid-19 pandemic wore on into a second year, 2021 will be remembered as when the world mounted the largest vaccination drive in history. But while new vaccines and other tools for fighting the coronavirus boosted hopes for a return to normalcy, the year also saw the emergence of new variants with names like Delta and Omicron, which have continued to spread and trigger massive disruptions.