WASHINGTON—Fully vaccinated U.S. citizens and permanent residents will be allowed into Canada as of Aug. 9, joined by the rest of the world Sept. 7, federal officials announced Monday as the country prepares to lower border barriers that were erected to limit the spread of COVID-19. Officials say the 14-day quarantine requirement will be waived beginning the second week of August for eligible travellers who are currently residing in the United States and have received a full course of a COVID-19 vaccine approved for use in Canada. The move comes two weeks after the Canada Border Services Agency began waiving quarantine rules for fully vaccinated Canadian citizens and permanent residents. It remained unclear Monday if or when the Biden administration plans to reciprocate for visitors to the U.S. “This preliminary step allows for the government of Canada to fully operationalize the adjusted border measures ahead of Sept. 7, 2021, and …