Question: A 27-year-old patient of mine recently learned she is pregnant. She took the influenza vaccine offered at work when she was 7 weeks pregnant. Is her fetus at risk of malformations?
Answer: No evidence indicates that killed influenza vaccine is teratogenic, even if given during the first trimester. Since 1996, Health Canada's Centre for Disease Control and Prevention has recommended that pregnant women in their second and third trimesters be vaccinated. This should not be interpreted as evidence that the vaccine is teratogenic in the first trimester because such evidence does not exist.