USPharmacist | Weekly News Update



Advertisement Advertisement	October 15, 2014 Common Side Effects of Flu Vaccine: Not What Many Fear Atlanta—Pharmacists deal with it all the time: People who refuse to get an influenza vaccine because they are fearful of getting the flu or flu-like symptoms. The truth: The chances of those side effects occurring in adults range from nil to highly unlikely. That’s according to the latest data from the CDC. The inactivated influenza vaccines (IIV), administered as a shot, fairly commonly causes pain, redness, and swelling at the injection site, but, according to the CDC, “Systemic events can occur after IIV but are usually mild and self-limited. IIV (which contains inactivated virus) cannot cause influenza.” While up to 64% of those receiving a flu shot have some pain at the injection site, it usually resolves in less than 2 days without treatment, according to a new CDC vaccine safety summary for clinicians. Fever, malaise, myalgia, and other systemic symptoms that can occur after vaccination with IIV usually affect those who have had no previous exposure to the influenza virus antigens in the vaccine, such as young children. In adults, the rate of having those flu-like symptoms is no greater than with a placebo injection, public health officials point out. The CDC did caution that ocular or respiratory symptoms such as red eyes, hoarseness, or cough have occasionally been reported within 24 hours after IIV administration in some studies but are typically mild and resolve quickly without specific treatment. As with all vaccines, immediate hypersensitivity reactions—ranging from hive to angioedema to anaphylaxis—can occur in rare cases. Other unusual side effects include an increased risk for febrile seizures in young children, detected with the 2010-2011 IIV but not during the 2012-2013 season, and temporally associated Guillain–Barré Syndrome (GBS) cases, which have been reported periodically. No clear link has been determined between GBS and flu vaccine, however. In addition to avoiding the vaccine in people with severe allergy to eggs or who reported past adverse events, IIV should not be administered within 6 weeks of a previous dose of an influenza vaccine or in those who have a moderate or severe acute illness with or without a fever, according to the CDC, which added that patients who had been hospitalized with an acute illness but who were well enough to be discharged can be vaccinated. The live, attenuated influenza vaccine (LAIV), which is administered as an intranasal vaccine and replicates in the nose, is now all in quadrivalent formulation. In clinical trials, quadrivalent LAIV had a similar safety profile as trivalent LAIV but generated slightly more reports of fever after the first dose in children 2 to 8 being vaccinated for the first time. Rhinitis and nasal congestion occurred more commonly after LAIV than IIV or placebo in adults and children, clinical trials indicated. Fever in children and sore throat in adults also are common adverse reactions, according to public health officials. A clinical trial showed increased rates of wheezing in children 6 through 23 months with LAIV, which is not approved for that age group, than with IIV. Wheezing rates did not differ between types of immunization in older children. Flu vaccine is not recommended for children younger than 6 months old. In adults, headache, sore throat, tiredness/weakness, muscles aches, cough, chills, and sinusitis occurred more often with LAIV than an intranasal placebo. The CDC cautioned that LAIV should never be administered to children younger than 2 or adults 50 or older, those with known allergies to influenza vaccines or eggs, children or adolescents receiving aspirin or other salicylates, pregnant women, patients with immunodeficiency diseases or immunosuppressed states such as HIV, children 2 to 4 years of age with asthma or wheezing in the last 12 months, or anyone who has taken influenza antiviral medications within the previous 48 hours. For recombinant influenza vaccine (RIV), first made available as a trivalent formulation (RIV3) in 2013, the most common injection-site reaction was pain, affecting more than 37%, in clinical trials. The most common systemic adverse reactions, meanwhile, were headache and fatigue, affecting more than 15%, as well as myalgia, affecting 11%. The safety and effectiveness of RIV3 have not been established in pregnant women, nursing mothers, children, or adults 50 years of age and older, according to the CDC. Click here for October 15, 2014 USP Weekly News Update.
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