The Centers for Disease Control and Prevention (CDC) is encouraging everyone over the age of 6 months without a contraindication to get vaccinated for the coming flu season. The Advisory Committee on Immunization Practices (ACIP) has recently updated their 2013 recommendations to take into account the new 2014–2015 influenza vaccines.
What are the 2014–2015 flu vaccines composed of?
Trivalent influenza vaccines will contain hemagglutinin derived from an A/California/7/2009 (H1N1)-like virus, an A/Texas/50/2012 (H3N2)-like virus, and a B/Massachusetts/2/2012-like (Yamagata lineage) virus.
Quadrivalent influenza vaccines will contain these antigens, and also a B/Brisbane/60/2008-like (Victoria lineage) virus.
These strains are identical to those found in the 2013–14 vaccine.
No change in strains, how does this change the number of doses required for children?
Children 6 months to 8 years of age who have never been vaccinated with the influenza vaccine still need 2 doses (≥4 weeks apart) in order to optimize immune response. However, given that the strains in 2014–15 vaccine are identical to those of 2013–14, children in this age group who have previously received ≥1 dose of 2013–14 only need 1 dose of 2014–15.
To determine the right number of doses, previous receipt of vaccine containing 2009 influenza A (H1N1) pandemic antigen (included in monovalent pandemic vaccine during 2009–10 and in seasonal influenza vaccines since the 2010–11 season) should also be considered. Children who have received ≥2 doses of seasonal influenza vaccine since July 1, 2010; or ≥2 doses of seasonal influenza vaccine before July 1, 2010, and ≥1 doses of monovalent 2009 (H1N1) vaccine; or ≥1 doses of seasonal influenza vaccine before July 1, 2010, and ≥1 doses of seasonal influenza vaccine since July 1, 2010 only require 1 dose of 2014–15 vaccine.