ATLANTA -- Two of the three strains covered by the seasonal influenza vaccine are changing for the upcoming season, and with that change comes a new dosing algorithm for children.
The trivalent inactivated vaccine will still contain the 2009 pandemic H1N1 strain, but the H3N2 and B strains will be replaced. The H3N2 component is changing from A/Perth/16/2009 to A/Victoria/361/2011, and the B component is changing from the Victoria-lineage B/Brisbane/60/2008 to the Yamagata-lineage B/Wisconsin/1/2010.
In part because of those changes, the dosing algorithm for children ages 6 months through 8 years has been modified at a regular meeting of the Advisory Committee on Immunization Practices (ACIP) at CDC headquarters here.
For the 2011-2012 season, two doses of the seasonal vaccine separated by at least 4 weeks were recommended for children who did not receive at least one dose of the 2010-2011 seasonal vaccine or who had unknown vaccination status. Children who did receive at least one dose of the 2010-2011 vaccine required only one dose of the 2011-2012 vaccine.
The dosing algorithm for the 2012-2013 season for children ages 6 months through 8 years, adopted by a unanimous vote, is the following:
- Children who have never received flu vaccine -- or for whom vaccination history is unknown -- should receive two doses of vaccine separated by at least 4 weeks.
- Among children who have received the seasonal flu vaccine previously, those who did not receive a total of at least two doses of seasonal vaccine since July 2010 -- or for whom the exact history since July 2010 is unknown -- should receive two doses of this year's vaccine separated by at least 4 weeks.
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Among children who have received the seasonal flu vaccine previously, those who have received a total of at least two doses of seasonal vaccine since July 2010 need only one dose of this year's vaccine.
There was some discussion about another option that would take into account the use of the monovalent H1N1 vaccine during the pandemic, but concerns were raised about complicating dosing decisions, and that option was voted down. In addition, the more detailed algorithm would not have been concordant with guidance that is being finalized by the American Academy of Pediatrics (AAP).
"Two recommendations not harmonized between the AAP and ACIP are going to throw clinicians into a tizzy," said ACIP member S. Michael Marcy, MD, of the University of Southern California and the University of California Los Angeles. "I just don't think that's a good idea at all because it implies that one or the other doesn't have all the facts or isn't making the appropriate recommendation."
The meeting marked the 1-year anniversary of a change in recommendations that removed egg allergy as a contraindication to influenza vaccination, and it does not appear that the modification affected the rate of allergic reactions, according to data from the Vaccine Adverse Event Reporting System (VAERS).
During the 2010-2011 flu season -- before the change -- there were 15 non-anaphylactic reactions associated with the seasonal vaccine. In 2011-2012, there were also 15.
In terms of anaphylaxis, there were three cases in 2010-2011 and no cases in 2011-2012.