H1N1 Virus: Implications for Rheumatology

As the fall begins, both rheumatologists and patients are concerned about the impact of the seasonal influenza virus. This year, there is the additional worry about the impact of the novel 2009 H1N1 (swine) flu virus. Rheumatologists have become accustomed to recommending, or administering seasonal, influenza vaccines, as many of our patients meet the guidelines for annual vaccination. The guidelines for 2009 H1N1 flu vaccination are similar, but not exactly the same.. The approach to the swine flu, and particularly vaccination strategies, has been changing rapidly; readers are cautioned to consult the CDC and FDA Web sites for any updates.

Seasonal Influenza Vaccines: Seasonal influenza occurs in the U.S. during the late fall to early spring period, and its associated morbidity and mortality has led to recommendations to immunize high-risk groups (children)

Novel Influenza (2009 H1N1) Strains: April 2009 brought the first reports of a novel influenza A (H1N1) virus causing human infections. Termed swine flu because this virus is endemic in pigs, it is distinct from the human influenza A (H1N1) viruses previously in circulation. Therefore, most individuals have no pre-existing antibodies to its key surface epitopes. Several companies are developing vaccines directed against this novel H1N1 influenza A and these will be available by mid-October 2009. It appears that a single injection will be adequate and will confer protection 8-10 days after vaccination. The vaccines themselves are made using the same process used to produce seasonal influenza vaccines, so that adverse reactions are not anticipated to be any different. Seasonal influenza vaccine and H1N1 vaccine may be administered at the same time. A live, attenuated H1N1 vaccine is expected to be available, but its use should be subject to the same restrictions as the seasonal live, attenuated influenza vaccine.

Adverse Effects: Because influenza vaccines are manufactured with chicken eggs, they are contraindicated in patients with a history of anaphylactic reactions to eggs or egg proteins. Thimerosal is used as an antibacterial in multidose vials of influenza vaccine. Single dose vials and LAIV sprays do not contain thimerosal. Vaccines administered to children <6>

Recommendations for Vaccination and Management of H1N1: The groups at risk for H1N1 infection and complications are similar to those at risk with the seasonal influenza virus, and recommendations for vaccination are correspondingly similar. Three specific groups likely to be seen by rheumatologists should receive H1N1 vaccine when available:

• Patients with inflammatory arthritis and other systemic inflammatory diseases


• Patients receiving immunosuppressive medications, including steroids, non-biologic and biologic DMARDs


• Patients with multiple chronic medical conditions, such as asthma, diabetes, heart disease, or malignancy, that put them at risk for influenza complications, including osteoarthritis patients with one of these conditions

In addition, pregnant women, health care and emergency response workers, young children age >6 months to 18, young adults age 19-24, and those who live with or care for children < href="http://www.cdc.gov/h1n1flu/vaccination/statecontacts.htm">http://www.cdc.gov/h1n1flu/vaccination/statecontacts.htm. The vaccine is provided free, but practitioners may bill for administration (http://www.cms.hhs.gov/MLNMattersArticles/downloads/se0920.pdf). The AMA recently released new CPT codes to bill for the administration of 2009 H1N1 influenza vaccination, effective immediately. See http://www.ama-assn.org/ama/pub/h1n1/resources/cpt-codes.shtml for details.

Managing Infected Individuals: Persons with suspected 2009 H1N1 influenza or seasonal influenza who present with an uncomplicated febrile illness generally do not require treatment. Those who do get sick should be advised to avoid work, school or travel until 24 hours after they become afebrile without fever reducing medications. The 2009 H1N1 strain appears to be sensitive to oseltamivir (Tamiflu®) and zanamivir (Relenza®); either medication may be used, although zanamivir is not recommended for persons with asthma or underlying respiratory disease. Antiviral therapy is appropriate for anyone hospitalized with suspected influenza or anyone at high risk for influenza complications, including children <5>65 years of age, pregnant women, and those with chronic illnesses or receiving immunosuppressive medications. When the clinical presentation is consistent with influenza, antiviral therapy should not be delayed by waiting for laboratory confirmation. Antiviral therapy should be initiated early, preferably within 48 hours of symptoms onset and continued for five days. Empiric therapy based on telephone contact with high-risk individuals may be considered. Antiviral therapy for individuals exposed to someone with confirmed or presumed H1N1 infection may be appropriate for patients in high-risk groups, but early identification of symptoms and initiation of antiviral treatment at that time (e.g., watchful waiting) is another option.