Flu season’s almost here: Are you ready?

Chemoprevention is now being deemphasized because of a concern for possible development of antiviral resistance. It should be considered for those in the high-risk categories (TABLE 2) with a documented exposure.⁷

Which antiviral to use will depend on which influenza strains are circulating and their resistance patterns. So far, H1N1 has remained largely sensitive to both neuraminidase inhibitors: oseltamivir and zanamivir. However, oseltamivir resistance has been documented in a few cases and will be monitored carefully.

Family physicians will need to stay informed by state and local health departments about circulating strains and resistance patterns. The latest Centers for Disease Control and Prevention (CDC) guidance on antiviral therapy can be consulted for dosage and other details on the 4 antiviral drugs licensed in the United States.⁷

What you must know about vaccine safety

Because of increasing public awareness of safety issues, family physicians will frequently need to address patients’ questions about the safety of this year’s vaccine. Last year, multiple reporting systems including the Vaccine Adverse Event Reporting System (VAERS), Vaccine Safety Datalink (VSD) Project, the Defense Medical Surveillance System (DMSS), and others, extensively monitored adverse events that could potentially be linked to the H1N1 vaccine.⁸ Three so-called weak signals—indications of a possible link to a rare, but statistically significant adverse event—were received.

The 3 signals were for Guillain-Barré syndrome (GBS), Bell’s palsy, and thrombocytopenia/idiopathic thrombocytopenic purpura. The status of the investigation of each potential link to the vaccine can be found on the National Vaccine Advisory Committee (NVAC) safety Web site at http://www.hhs.gov/nvpo/nvac/reports/index.html.

The GBS signal has been investigated the most aggressively because this adverse reaction has been linked to the so-called swine flu vaccine of 1976. One analysis has been published in the Morbidity and Mortality Weekly Report.⁹ Whether GBS has a causal link to the H1N1 vaccine remains in doubt. In the worst-case scenario, if causation is determined, it appears that the vaccine would account for no more than 1 excess case of GBS per million doses.⁹

In Western Australia, there has been a recent report of an excess of fever and febrile seizures in children 6 months to 5 years of age, and fever in children 5 to 9 years of age who received seasonal influenza vaccine. The rate of febrile seizures in children younger than age 3 was 7 per 1000, which is 7 times the rate normally expected. These adverse reactions were associated with only 1 vaccine product, Fluvax, and Fluvax Junior, manufactured by CSL Biotherapies.¹⁰ The CSL product is marketed in the United States by Merck & Co. under the brand name Afluria.

The Advisory Committee on Immunization Practices (ACIP) has issued the following recommendations:¹¹

• Afluria should not be used in children ages 6 months through 8 years. The exception: children who are ages 5 through 8 years who are considered to be at high risk for influenza complications and for whom no other trivalent inactivated vaccine is available.
• Other age-appropriate, licensed seasonal influenza vaccine formulations should be used for prevention of influenza in children ages 6 months through 8 years.

High-dose vaccine for elderly patients

A new seasonal influenza vaccine (Fluzone High-Dose, manufactured by Sanofi Pasteur) is now available for use in people who are 65 years of age and older.¹² Fluzone High-Dose contains 4 times the amount of influenza antigen as other inactivated seasonal influenza vaccines. Fluzone High-Dose vaccine produces higher antibody levels in the elderly but also a higher frequency of local reactions. Studies are being conducted to see if the vaccine results in better patient outcomes. ACIP does not state a preference for any of the available influenza vaccines for those who are 65 years of age and older.¹²

Children younger than age 9: One dose or two?

The new recommendations for deciding if a child under the age of 9 years should receive 1 or 2 doses of the vaccine run counter to the trend for simplification in influenza vaccine recommendations. The decision depends on the child’s past immunization history for both seasonal and H1N1 vaccines. To be fully vaccinated with only 1 dose this year, a child must have previously received at least 1 dose of H1N1 vaccine and 2 doses of seasonal vaccine. FIGURE 2 illustrates the process you need to go through to make the dosage choice. When the child’s immunization history is unknown or uncertain, give 2 doses, separated by 4 weeks.⁴

FIGURE 2
Children younger than 9: Ask 4 questions