OTTAWA, Feb 9 (Reuters) - Canada will allow medical officials to extract an extra sixth dose of Pfizer Inc’s COVID-19 vaccine from each vial, up from five currently, the health ministry said on Tuesday. Supriya Sharma, a senior advisor at the ministry, told reporters that the United States and some European Union nations had already made similar changes. Canada’s government is under pressure over the slow pace of vaccinations, caused in part by a temporary reduction in supplies from Pfizer. (Reporting by David Ljunggren)