Flu vaccine recommendations for young children updated

Young children who were not immunized against the 2009 influenza A(H1N1) will need two doses of the 2010-11 seasonal flu vaccine to assure they are protected, according to the Advisory Committee on Immunization Practices.

The seasonal vaccine will include a pandemic 2009 H1N1 virus, as well as an A/Perth/16/2009 (H3N2)-like virus and a B/Brisbane/60/2008-like virus.

The ACIP, a 15-member committee that advises the Centers for Disease Control and Prevention on vaccine issues, released the new recommendation for children age 6 months to 8 years on June 24 at a meeting in Atlanta.

Some committee members raised concerns that the new recommendation would complicate influenza vaccination for physicians. As an example, they asked what doctors should do if parents can't remember whether their child received at least one dose of the H1N1 vaccine.

In such instances, the committee recommends administering two doses of the 2010-11 seasonal flu immunization.

"The underlying principle is that all children age 6 months through 8 years need to have at least two doses of the 2009 H1N1 antigen," said Anthony Fiore, MD, MPH, medical epidemiologist for the CDC's Influenza Division.

He said children could receive the two doses from the monovalent H1N1 vaccine or the upcoming trivalent seasonal flu immunization. The CDC advises that children younger than 10 get two doses of the 2009 H1N1 antigen. He added that children who got two doses of the H1N1 vaccine still need a seasonal 2010-2011 trivalent dose.

Dr. Fiore said several studies conducted in 2009 and 2010 indicate that young children often need two doses of a vaccine containing the 2009 H1N1 antigen. The studies showed 44% to 93% of children age 3 to 9 had antibody titer levels considered protective after receiving one dose of H1N1.

He said administering a second dose of the H1N1 antigen to infants and young children provides 80% or more with protection.

H1N1 vaccine safety

The ACIP also discussed the safety of the H1N1 vaccine, focusing on reported cases of Bell's palsy, Guillain-Barré syndrome and seizures in patients following immunization. Presenters said there is no significant difference in safety between the H1N1 and seasonal flu vaccines. Researchers are continuing to monitor reported effects of the H1N1 immunization.

As of June 24, H1N1 had infected 60 million Americans, about 20% of the population, according to the CDC. Nearly 12,000 died, and about 265,000 were hospitalized. H1N1 disproportionately affected young people, who are not typically casualties of seasonal flu, which kills about 36,000 Americans each year.

Although there now is little H1N1 and seasonal flu activity in the U.S., Dr. Fiore expects a 2009 H1N1-like virus to circulate during the 2010-11 season.

During the ACIP meeting, the Food and Drug Administration updated committee members on the virus that was found in the nation's two rotavirus vaccines in the spring. Researchers determined that porcine circovirus type 1, identified in GlaxoSmithKline's Rotarix, includes complete virus genomes and can infect swine cells in culture, said Wellington Sun, MD, director of the FDA's Division of Vaccines and Related Products Applications.

In Merck's RotaTeq, researchers found fragments of PCV1 and porcine circovirus type 2, Dr. Sun said. The FDA is continuing to investigate the PCV components found in the vaccines.

"There is no evidence at this time that PCV or PCV DNA in U.S.-licensed vaccines poses a safety risk," Dr. Sun said.