July 29 (Reuters) - Major League Soccer said on Thursday its three Canadian clubs that set up temporary bases in the United States late in 2020 due to border restrictions associated with COVID-19 can host all their remaining 2021 home matches in Canada. MLS said the Public Health Agency of Canada and Minister of Immigration approved a National Interest Exemption that outlines protocols allowing for all league players to participate in cross-border matches with Toronto, Montreal and Vancouver Whitecaps. According to MLS, all travelling players and staff will continue to undertake COVID-19 testing prior to, and upon arrival into Canada, regardless of their vaccination status. Individuals who are partially vaccinated, or unvaccinated, will be required to observe a modified quarantine and upon receipt of a negative COVID-19 test would only be able to participate in work activities. The three Canadian teams finished the 2020 season at their "home" bases in the United States and remained there for the start of the 2021 season in April. Toronto and Montreal started the 2021 season in Florida while Vancouver played their home games out of Utah. Toronto and Montreal hosted a select number of matches in their actual home cities earlier in July and MLS said last week all three Canadian clubs were cleared to host August home games in their respective markets. MLS also said 96% of all Tier 1 individuals, a group that includes players and club staff members that work closely with the teams, are fully vaccinated.