Several panelists said that information on the cost-benefit of a quadrivalent vaccine was crucial, because increased cost could affect immunization rates. Dr. Reed acknowledged the limitations of the model used in the CDC's analysis, which focused on the public health impact of a quadrivalent vaccine and did not include an analysis on the cost-benefit, did not consider potential adverse events associated with adding a second B component, and did not analyze different age groups separately, data that other panelists agreed were needed.
Several panelists also referred to the limited data on the effectiveness of the B component of the influenza vaccine. Because there are “very, very few pure” influenza B years, “we get used to equating influenza B effectiveness with what we know about influenza A effectiveness … but that may be totally erroneous,” said panelist Dr. Theodore Eickhoff, professor emeritus in the division of infectious diseases, University of Colorado Health Sciences Center, Aurora.
Referring to the two cocirculating B virus lineages over the past few seasons, Dr. Roland Levandowski, an infectious disease specialist in Bethesda, Md., remarked, “If we go to the trouble of immunizing against” two influenza A strains, “then we should have a vaccine with coverage against both B strains.”
At the close of the meeting, the panel chair, Dr. John Modlin, professor of pediatrics at Dartmouth-Hitchcock Medical Center, Lebanon, N.H., summarized the attitude of the panel regarding the prospect of a quadrivalent vaccine as “a qualified thumbs-up.”
A model that incorporates age-specific influenza rates, morbidity, and other factors for determining the public health impact of a quadrivalent vaccine is clearly needed, Dr. Modlin said. “Hopefully, the committee has sent the message it would like to see the CDC model work continued,” he added.