“NACI recommends that AstraZeneca COVID-19 vaccine should not be used in adults under 55 years of age at this time while the safety signal of Vaccine-Induced Prothrombotic Immune Thrombocytopenia (VIPIT) following vaccination with AstraZeneca COVID-19 vaccine is investigated further,” NACI said in a statement on Monday.

The updated guidance comes as European researchers have purported that an autoimmune response to AstraZeneca’s vaccine is behind the blood clots that have forced the suspension of inoculation with the vaccine in several European Union countries.

Despite the advisory committee’s warning, Canadian federal health regulators indicated to reporters that they don’t plan on changing the current federal guidance that says the AstraZeneca vaccine is safe and effective for adults over the age of 18.

“There hasn’t been enough data to show that we should make a change to the way that the vaccine is used or changes to the labeling,” Health Canada Chief Medical Advisor Supriya Sharma.

Deputy Chief Public Health Officer Dr. Howard Njoo said that those who have been vaccinated with the AstraZeneca vaccine should seek immediate medical attention if they develop symptoms including, chest pain, leg swelling and shortness of breath, between four and 16 days after being inoculated. Njoo said those who have been vaccinated more than 20 days ago have no cause for concern.

Shadow Minister of Health, Michelle Rempel Garner, during a press briefing called for greater transparency from Prime Minister Justin Trudeau and to explicitly say if Health Canada will accept the advisory committee’s recommendation.

However, a number of provinces, including Alberta, Manitoba and Newfoundland and Labrador, have announced that they are temporarily halting vaccination with the AstraZeneca shots effective immediately.

In its statement, NACI said a decision on the second vaccine dose for those already vaccinated with the AstraZeneca shot should be made based on the “latest evidence and research.”

Canadian health regulators last week issued a disclaimer regarding blood clots that may potentially form in individuals who vaccinate with the AstraZeneca coronavirus vaccine.