ACIP updates recommendations for flu vaccines

In a departure from current recommendations, the CDC’s Advisory Committee on Immunization Practices recommended that children aged 6 months to 9 years who have not been immunized with the 2009 H1N1 monovalent vaccine receive two doses of seasonal influenza vaccine.

At the committee meeting held today in Atlanta, the Influenza Vaccine Work Group presented updated immunogenicity data regarding both the seasonal and monovalent influenza vaccines.

The monovalent influenza vaccine produced some seropositivity in children and adults, according to Anthony Fiore, MD, MPH, of the CDC, but study results on how long the vaccine provides protection are lacking.

Research on the seasonal influenza vaccine’s immunogenicity reveals that antibody titers remain lower in young children after immunization when compared with older peers and adults. Other studies indicate that the prevalence of immunoglobulin M (IgM) titers are again lower in children aged 3 to 9 years, Fiore noted, with this number declining even further in children aged 6 to 36 months.

Fiore also cited data from an NIH study that indicated around 20% of patients responded to one vaccine while 80% responded to two doses, leading the work group to conclude that two doses would optimize coverage and protection against the disease.

In light of the new research, the Influenza Vaccine Work Group also suggested that the ACIP reconsider its position on dosing recommendations for children aged 6 months to 8 years as they had lower levels of immunogenicity after vaccination.

“The implication is that some children recommended to receive a single dose of seasonal flu vaccine might benefit from getting two doses of H1N1 antigen, and after two doses, many children would be protected,” Fiore said.

He also reported that doubling the vaccine dose did not increase reactivity or induce unexpected adverse reactions.

The panel also discussed the safety of the monovalent influenza vaccine. A variety of topics were addressed, including the potential for an increase in incidence of Guillain-Barré syndrome, deaths, hospitalizations and other serious conditions. Presenters affirmed that data did not show any difference in safety profiles between the monovalent and seasonal influenza vaccines.

“I think we have incredible data on the safety of this vaccine, and I hope everyone who is listening is reassured by the data presented here today,” said ACIP chair Carol J. Baker, MD. — by Melissa Foster

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