Canada’s National Advisory Committee on Immunization recommended Monday that the AstraZeneca Covid-19 vaccine should not be used in adults under age 55 while rare cases of serious blood clots following vaccination are being investigated, according to a release from the committee. The rare cases of serious blood clots, known as vaccine-induced prothrombotic immune thrombocytopenia (VIPIT), have recently been reported in Europe following post-licensure use of the AstraZeneca vaccine, primarily in women under the age of 55. According to the vaccine committee, the rate of this adverse event is still to be confirmed and information is being gathered to be more accurate. “Following population-based analyses of VIPIT assessing risk of COVID-19 disease by age, and considering that alternate products are available (i.e., mRNA vaccines), from what is known at this time, there is substantial uncertainty about the benefit of providing AstraZeneca COVID-19 vaccine to adults under 55 years of age given that the potential risks associated with VIPIT, particularly at the lower estimated rates,” committee officials said. As a precautionary measure, while Health Canada carries out an updated risk versus benefit analysis based on emerging data, the committee is recommending that the vaccine not be offered to adults younger than 55 but will continue to reassess based on “rapidly evolving evidence.” The committee said because the AstraZeneca vaccine was expected to only make up a small proportion of the Covid-19 vaccines available for use in Canada, vaccinations “will not be significantly delayed.” CNN reached out to the drugmaker for comment but didn’t get an immediate response. AstraZeneca’s development of the vaccine has hit multiple bumps, from news that two volunteers developed neurological symptoms last fall to a stall in the rollout of the vaccine in several European countries amid fears it might have caused blood clots. The European Medicines Agency has since said there’s no evidence the vaccine can cause blood clots. The agency’s executive director Emer Cooke said several weeks ago the agency had “come to a clear scientific conclusion: this is a safe and effective vaccine.” Cooke said the group did not find that the vaccine causes clotting, though it could not rule out definitively a link to a rare blood clotting disorder, of which seven cases have been reported out of several million doses given. She said the benefits of using the vaccine outweighed the risk. An agency committee “concluded that the vaccine is not associated with an increase in the overall risk of thromboembolic events, or blood clots,” Cooke said. More than a dozen European countries had halted their use of the vaccine. Some nations have resumed vaccinations while others have continued their pauses. The World Health Organization has also said there is no relationship between the vaccine and common clotting disorders. Canada received a boost from the Biden administration in recent weeks when the two countries struck a deal that will see the US release 1.5 million of its AstraZeneca doses to Canada at some point. The US is stockpiling the AstraZeneca vaccine until it receives FDA authorization, which is not likely until at least next month. Canada has reported almost 970,000 presumed or confirmed cases of the coronavirus since the start of the pandemic and has recorded more than 22,000 deaths.