2009 pandemic influenza A (H1N1) and vaccine failure in pregnancy.

BACKGROUND: Emerging data suggest that pregnancy conveys high risk for severe complications from the 2009 pandemic influenza A virus (2009 H1N1) infection. CASE: We describe an infected pregnant woman with critical illness owing to acute respiratory distress syndrome despite previous vaccination. Early serologic testing indicated absent immunity, followed 11 days later by a robust immune response. The patient required mechanical ventilation for 11 days, but ultimately improved, and was discharged home on hospital day 14. CONCLUSION: With the expectation that 2009 H1N1 will continue to cause disease in the immediate future, the virus has been included as a component of the 2010-2011 seasonal influenza vaccine. Vaccination of pregnant women is strongly encouraged. However, regardless of vaccination history, clinicians should remain vigilant for 2009 H1N1 infection when the virus is in circulation, and should not delay antiviral treatment of pregnant women with suspected influenza.