Immunization - Key Points

Key Points

Current Canadian recommendations advocate universal immunization of pregnant women in any trimester against influenza and influenza immunization of the caregivers and family of young infants

Pregnant women are at increased risk of influenza-related hospitalization and serious complications, including mortality

Pregnancy is associated with significant cardiovascular and respiratory demands, as evidenced by increased in stroke volume, heart rate, and oxygen consumption

More recent studies have shown an increase in influenza-related hospitalization of healthy pregnant women, with seasonal influenza occurring at the rate of 1 per 1000 or 0.1%

The risks were in fact calculated to be equivalent to those of non-pregnant women with high-risk conditions, for whom immunization has traditionally been recommended

Influenza vaccine is not teratogenic

Large studies have not found such an association between influenza immunizations and pregnancy loss or other adverse pregnancy outcomes
Passive surveillance has not revealed any safety concerns about using inactivated influenza vaccine in pregnancy over decades, and surveillance following the use of pandemic influenza A (H1N1) vaccines in more than 100 000 pregnant women in Canada and more than 488 000 pregnant women in Europe also did not reveal any safety concerns

Immunization in pregnancy also protects the fetus and newborn after birth, which can be accomplished with passive immunity (transfer of maternal antibodies)

RCT evidence demonstrates that the administration of the influenza vaccine during pregnancy reduces febrile influenza-like illness in pregnant women by over 30% and also reduces proven influenza infections in 0- to 6-month-old infants by 63%

Infants born to women who had received the influenza vaccine were less likely to be born small for gestational age (SGA)

Data also demonstrate a reduction in the rate of stillbirth among mothers who have received the influenza vaccine during pregnancy