The Boston Athletic Association (B.A.A.) said that runners who received doses from two different vaccine brands – which many Canadians have – must also wait for test results before being admitted to the event.

"Prior to bib number pick-up, Boston Marathon participants will be required to either produce proof of a complete vaccination series of a World Health Organization (WHO)-certified vaccine or produce a negative COVID-19 test, which will be administered on site in a Boston Marathon medical tent," said the B.A.A. in a statement, as reported by Canadian Running.

"A WHO certified vaccine is considered to be both doses of a two-dose vaccine, or one dose of a singular dose vaccine.

"If you do not have one of the previously mentioned WHO certified vaccines, you will need to be tested at the Boston Marathon medical tent.

"If you have received a mixed dose of two different vaccines, you will need to be tested at the Boston Marathon medical tent.

"Vaccine verification will occur Friday, October 8 through Sunday, October 10 in co-ordination with the Boston Marathon Expo hours.

"Participants may bring an original paper copy, digital copy, photocopy, or photo of their vaccination proof."

Organisers are keen to ensure that the race is coronavirus-free and are encouraging participants to receive inoculations.

"The B.A.A. will work with a third-party testing provider for test administration and results tracking," the statement continued.

"Testing will begin no earlier than 72 hours prior to participant start times on Monday, October 11.

"Exact hours, locations, and additional details will be communicated directly to all participants.

"Tested participants will not receive immediate access to enter the Boston Marathon Expo for bib number pick-up and will be required to wait for confirmation of test results.

"Testing will take about 30 minutes to complete and receive results.

"The fastest path to pick up numbers for the 125th Boston Marathon is being fully vaccinated."

The Boston Marathon was cancelled for the first time in its history in 2020 due to the coronavirus pandemic.

The Massachusetts race, on October 11, is set to be the fourth of the World Marathon Majors in 2021, all of which are scheduled to take place within a matter of weeks.

The Berlin Marathon took place on September 26 while the London Marathon gets underway on Sunday (October 3) and the Chicago Marathon begins a week later on October 10.

The New York City Marathon is then scheduled for November 7 and the postponed Tokyo Marathon for March 6 2022.