ATLANTA — Children aged 6 months to 9 years of age who did not receive two doses of vaccine the first time they were immunized against influenza should receive two doses the following season, the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices recommended at its winter meeting.
To ensure an adequate immune response, children aged 6 months through 9 years receiving influenza vaccine for the first time are supposed to receive two doses given at least a month apart. But for a variety of reasons, some children receive only one dose. Two studies published in 2006 suggest that these children would be better protected against influenza if they receive two doses the following year, Dr. Anthony Fiore of the CDC's National Center for Immunization and Respiratory Diseases, told the committee.
In one study, when the influenza B antigen was changed for the second season, children who only received one dose in their first season of being vaccinated and one dose in their second season had decreased immunologic response to the influenza B antigen, compared with children who received two doses (Pediatrics 2006;118:e579–85).
The other study showed that, in consecutive seasons when the influenza vaccine antigens were unchanged, effectiveness against influenzalike illness in the second season was significantly less for 6− to 21-month-old children being vaccinated for the first time who received one dose in both seasons, compared with 6− to 21-month-olds who received one dose in their first season and two doses in their second season (J. Pediatr. 2006;149:755–62).
The new ACIP recommendation brings it in line with the American Academy of Pediatrics, which issued the same guideline in October 2006. The American Academy of Family Physicians, which usually follows ACIP's recommendations, will likely change its advice as well, AAFP coliaison Dr. Doug Campos-Outcalt said in an interview.
That recommendation was the only major change that will appear in the ACIP's 2007 influenza statement, which does not add any new age or risk groups for routine immunization, compared with 2006. The statement will continue the advice from last season against the use of amantadine and rimantadine for the treatment or prevention of influenza because resistance to the antivirals among H3N1 strains in the United States was more than 30% this season, Dr. Fiore noted.
The statement will, however, contain some new language. More direct wording will address the lack of scientifically conclusive evidence demonstrating harm from exposure to thimerosal preservative-containing vaccine, and the recommendation that any age- and risk-factor appropriate preparation is acceptable depending on availability. Prior to its vote on the influenza immunization statement, the ACIP heard a presentation by Dr. Jay Lieberman summarizing available data on thimerosal (see accompanying story).
Reinforcement of the need for health care workers to be immunized against influenza will be included in the statement, which also will mention new recommendations from several professional societies that all facilities employing health care workers offer the vaccine and require a written declination for those who choose not to be vaccinated.
New language on the timing of influenza immunization will note that although the ideal time is late September and October, immunization efforts should continue through January and beyond. Peak influenza activity occurs in February or March in most seasons, Dr. Fiore said.
Pediatricians and family physicians who treat children should be aware that the ACIP is gearing up to expand its influenza vaccination recommendations beyond the current ages 6 months to 5 years to include all children aged 5–18 years. A meeting is planned for this summer to consider the scientific and implementation issues, with the goal of implementation for the 2008–2009 flu season, Dr. Ban Mishu Allos, the ACIP's influenza immunization task force chair, told the committee.
Dr. Deborah Wexler, chief of the Immunization Action Coalition, told the committee that universal annual childhood immunization against influenza is already a stated goal of several national, state, and regional professional health care groups.