Influenza vaccine programs and pregnancy: a need for more evidence.

Influenza viruses are the most common cause of seasonal respiratory morbidity in the world. Annual influenza vaccination is recommended for persons at high risk for serious disease. In the United States, in 2004, the Advisory Committee on Immunization Practices added all pregnant women to its high-risk list. In Canada, the National Advisory Committee on Immunization only includes pregnant women who have other underlying risk factors in the high-priority category for influenza immunization. This commentary provides an overview of maternal morbidity in pandemic and nonpandemic influenza seasons as well as a list of research questions whose answers are needed for evidence-based public health policy in this area.