Although the 2011-2012 influenza season was milder than usual and associated with fewer outpatient visits, lower hospitalization rates, and fewer pediatric deaths, practitioners should be aware that this virus is still the leading cause of vaccine-preventable deaths in children. Hopefully, practitioners are already providing influenza immunization utilizing the 2012-2013 vaccine, which contains the same influenza A (H1N1) antigen as the 2011-2012 seasonal vaccine but new influenza A (H3N2) and B antigens: These are A/California/7/2009 (H1N1)–like antigen, A/Victoria/361/2011(H3N2)–like antigen, and B/Wisconsin/1/2010–like antigen.
Here are the answers to some of the most common questions related to this year’s influenza season:
Dr. Mary Anne Jackson
• How many doses are recommended this year for children between 6 months through 8 years of age?
For a child in this age group who had two or more doses of seasonal vaccine since July 1, 2010, or in whom you can document one dose of a pandemic H1N1–containing vaccine and at least two seasonal vaccines from any season, only one dose is needed. All others in this age group should receive two doses. As always, those 9 years of age and older receive one dose of vaccine.
• Given recent data that suggested a slight increased risk of a febrile seizure following trivalent inactivated vaccine (TIV) in children less than 4 years, have vaccine recommendations changed?
A suggestion of an increased risk for febrile seizures in young children after TIV was noted in the United States in 2010-2011. This followed enhanced monitoring after the observation in Australia in 2010 of an association with an increased risk of febrile seizures (greater than or equal to nine per 1,000 doses) that were related to a particular influenza vaccine. (Afluria vaccine is approved for use in those greater than age 5 years, but current recommendations from the American Academy of Pediatrics and the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices (ACIP) state this vaccine should not be used in those less than 9 years of age. It could be considered for a high-risk patient between 5 through 8 years if no alternative TIV is available and after discussion of the seizure risk with parents.)
To further study this potential association, the CDC tracked more than 200,000 children in the United States who received TIV or PCV13 (Prevnar) vaccine at different visits or both together at the same visit. Rarely, a febrile seizure was noted in children less than 5 years who got TIV or PCV13 vaccine given at separate visits. Those 12- to 23-month-olds who received both at the same visit had a slightly increased risk for an uncomplicated febrile seizure in the 24 hours following vaccine receipt. This is the age group where febrile seizures peak in general and is equivalent to one excess seizure for every 2,000-3,000 vaccine doses. Based on this low risk and the uncomplicated course in such patients, coupled with the benefits of immunization, both the AAP and ACIP recommended no change in either the TIV or PCV13 vaccine policies. And remember that neither a prior febrile seizure history nor a preexisting seizure disorder is considered a contraindication for influenza vaccine.
• Who can get the intradermal formulation of influenza vaccine?
Fluzone Intradermal, which made its debut in the 2011-2012 season, is licensed for those 18-64 years of age, and is a preservative-free, trivalent inactivated influenza vaccine. It comes in a prefilled microinjection syringe, which for those who require TIV and are needle averse, may be preferred. Local reactions seen with intramuscular TIV (with the exception of pain), including redness, swelling, and itching at the site seem to be a bit more common with the intradermal product, but such reactions abate in 3-7 days. This vaccine could be utilized in an older adolescent who might opt for a vaccine that has a needle that is 90% shorter than the needle used for intramuscular injection of TIV.
• Is oseltamivir still the drug of choice to treat influenza?
Last year only 1.4% of strains were resistant to oseltamivir, and this year is expected to be the same. Treatment and prophylaxis dosing is the same as last year. The AAP and ACIP continue to emphasize early treatment for all children in high-risk groups who develop influenza, regardless of influenza immunization status. Treatment is also recommended for all who are ill enough to require hospitalization. For patients with influenzalike illness, the decision to treat should not be based on rapid antigen testing results. A negative test does not "rule out" influenza as commercially available tests are not sufficiently sensitive. You might want to check with your hospital to find out what other influenza testing is available in your locale.