The National Advisory Committee on Immunization is being asked to look into if there’s merit to delaying second doses of COVID-19 vaccines in an effort to get more Canadians vaccinated faster with first shots.

The request comes from the country’s top public health officer, Dr. Theresa Tam, after the U.K. said it’ll delay second doses of vaccines from Pfizer and AstraZeneca up to 12-weeks.

Pfizer’s is supposed to be given 21-days apart, while AstraZeneca’s 28-days apart.

Health Canada has not yet approved AstraZeneca’s vaccine candidate.

Pfizer says in a statement ultimately alternative dosing decisions are up to local health officials but that the company has no evidence protection after the initial dose remains in place after 21-days.

Dr. Tam says the immunization advisory panel’s being asked to provide analysis on what’s known about the dosing regimens, and what should be considered in deciding whether or not to delay second doses.