European Union’s top official expressed regret for creating a row with Britain last month when the bloc briefly considered applying an emergency restriction on exports of COVID-19 vaccines also to the U.K.’s Northern Ireland.Amid a dispute with Anglo-Swedish drugmaker AstraZeneca, the EU introduced tighter rules on exports of COVID-19 vaccines that could hit shipments to nations that rely on European factories for its vaccines, such as Canada and the United Kingdom.To implement its plan, EU officials thought about also introducing controls on exports to Northern Ireland from Ireland, which is part of the EU.That would have created a hard border.