What is the role of vaccination in the prevention of H1N1 influenza (swine flu)?

Updated: Apr 09, 2019
  • Author: Michael Stuart Bronze, MD; Chief Editor: Russell W Steele, MD  more...
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The 2009 influenza A (H1N1) monovalent vaccine was released in mid October. The immunization series consisted of 2 doses for children younger than 10 years, consisting of an initial dose and a booster to be administered several weeks later. Adults and children 10 years and older received a single dose. Targeted populations recommended to receive the 2009 H1N1 vaccine included pregnant women, household contacts and caregivers of children younger than 6 months, healthcare and emergency medical services personnel, children aged 6 months to 18 years, young adults aged 19-24 years, and persons aged 25 through 64 years with conditions associated with higher risk of medical complications from influenza. [41, 42]

A separate seasonal influenza vaccine was needed for the 2009/2010 influenza season because it was too late to incorporate the new strain into the regular influenza vaccine already in production. Now H1N1 is a component of the trivalent and quadrivalent influenza vaccines.

A 2011 CDC analysis reaffirms the importance of vaccinating pregnant women regardless of trimester and prompt treatment with a neuraminidase inhibitor (ie, within 2 d of symptom onset) if influenza occurs during pregnancy. [34]

There are only a limited number of studies that describe the safety of giving influenza vaccine to pregnant women. A 2012 study in Denmark found no evidence of an increased risk of fetal death associated with exposure to an adjuvanted pandemic A/H1N1 2009 influenza vaccine during pregnancy. [43]

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