Vaccines

BRUSSELS — The European Union is finalizing emergency legislation that will give it broad powers to curb exports for the next six weeks of Covid-19 vaccines manufactured in the bloc, a sharp escalation in its response to supply shortages at home that have created a political maelstrom amid a rising third wave on the continent.

Federal health officials and an independent oversight board accused AstraZeneca of presenting the world with potentially misleading information about the effectiveness of the company’s Covid-19 vaccine, an extraordinary blow to the credibility of a company whose product has been seen as critical to the global fight against the pandemic.

In a two-page letter to AstraZeneca and federal authorities on Monday, an independent panel of medical experts that was helping oversee the vaccine’s clinical trial in the United States said the company had essentially cherry-picked data that was “most favorable for the study as opposed to the most recent and most complete.”