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Influenzae Vaccine 2012-2013

Thursday, September 27, 2012 // Uncategorized

Influenza Vaccine for 2012-2013

 It is the flu vaccine season.  Here’s the summary on this season’s flu vaccine from an independent source, The Medical Letter.

The Medical Letter on Drugs and Therapeutics • October 1, 2012 (Issue 1400) p. 77

 
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Annual vaccination against influenza A and B viruses is the most effective method of preventing influenza and has been shown to decrease influenza illness and its complications. A new vaccine is available for the current season. Chemoprophylaxis and treatment of influenza was discussed in an earlier issue.1

VACCINE COMPOSITION — This year’s seasonal trivalent influenza vaccine contains the following three strains: A/California/7/2009 H1N1-like (derived from the pandemic 2009 influenza virus), A/Victoria/361/2011 H3N2-like, and B/Wisconsin/1/2010-like. The H1N1 strain is the same as in last year’s vaccine. The H3N2 and B strains are new this year.2

LIVE VS. INACTIVATED VACCINE — FluMist, the intranasal live attenuated influenza vaccine (LAIV), is recommended for use only in healthy, non-pregnant persons 2-49 years old. In children, the LAIV appears to be more effective than the trivalent inactivated vaccine (TIV).3 In adults, the TIV has been more effective.4

WHO SHOULD BE VACCINATED — The US Advisory Committee on Immunization Practices (ACIP) recommends annual influenza vaccination for everyone ≥6 months old who does not have a specific contraindication, including pregnant women.5 Vaccination of pregnant women not only protects them against influenza-associated illness, but also protects their newborn infants for up to the first 6 months of life.6,7

TIMING — Serum antibodies reach maximal levels in most adults about 2 weeks after influenza vaccination and generally persist for at least 6-8 months. The vaccine should be offered as soon as it becomes available through the end of the influenza season in May.

EFFECTIVENESS — The effectiveness of the seasonal vaccine in preventing influenza in healthy adults depends on the match between the vaccine and circulating strains. Vaccine effectiveness is highest when the match is close, but even when the match is poor, vaccination has been shown to reduce the risk of death from influenza.8 In addition, vaccination of children and adolescents can protect unvaccinated residents of the same community.9

ADVERSE EFFECTS — TIV – Except for soreness at the injection site, adverse reactions to TIV are uncommon. In clinical trials, Fluzone High-Dose and Fluzone Intradermal have caused more injection-site reactions than standard TIV vaccines.

During the 2010 influenza season in Australia, a vaccine formulation identical to Afluria was associated with an increased risk of fever and febrile seizures in children 6 months-4 years old and an increased risk of fever in children 5-8 years old. Afluria is licensed in the US for use in children ≥5 years old, but the ACIP recommends that it be used only in patients ≥9 years old.5

Rarely, influenza vaccination has been associated with Guillain-Barré syndrome, but the absolute risk is very low, and influenza infection itself has been associated with Guillain-Barré syndrome.10

LAIV – Rapid influenza diagnostic tests may be falsely positive if used within a week after FluMist vaccination. The intranasal LAIV is generally well tolerated, but can cause a runny nose, nasal congestion and a sore throat. It is not recommended for use in children <2 years old. Children <5 years old with recurrent wheezing and patients of any age with asthma may be at increased risk of wheezing after receiving FluMist.

Vaccinees may shed the vaccine-strain virus for a few days after vaccination, but person-to-person transmission has been rare, and serious illness resulting from transmission has not been reported. Healthcare workers and family members should avoid close contact with severely immunocompromised patients in protected environments for 7 days after vaccination with the live vaccine.

PRECAUTIONS AND CONTRAINDICATIONS — A history of a severe allergic reaction to any influenza vaccine is a contraindication to vaccination. Since both the live and inactivated vaccines are made from virus grown in eggs, hypersensitivity reactions to egg protein could occur. Persons being vaccinated who report a history of having had only hives related to egg exposure should receive TIV rather than LAIV, and should be observed for 30 minutes following vaccine administration for signs of an allergic reaction. Persons with a history of a more severe reaction to eggs should be referred for allergy evaluation before vaccination.11

DOSAGE — A 0.5-mL IM dose of TIV is recommended for adults and children ≥3 years old; 0.25 mL IM is recommended for children 6-35 months old. FluMist is given as a 0.2-mL dose (0.1 mL in each nostril). Fluzone Intradermal is given intradermally as a 0.1-mL dose using the supplied microinjection system.

Children 6 months-8 years old being vaccinated for the first time should receive two doses of seasonal vaccine at least 4 weeks apart. Children 6 months-8 years old who received 2 or more doses of seasonal vaccine since July 1, 2010 need only one dose this year; all other previously vaccinated children <9 years old should receive two doses this year.5

CONCLUSION — Seasonal influenza vaccine is effective in preventing influenza and should be offered to everyone ≥6 months old who does not have a specific contraindication.

1. Antiviral drugs for influenza. Med Lett Drugs Ther 2012; 54:1.

2. CDC. Vaccine virus selection for the 2012-2013 influenza season. Available at http://www.cdc.gov/flu/about/season/vaccine-selection.htm. Accessed September 16, 2012.

3. RB Belshe et al. Live attenuated versus inactivated influenza vaccine in infants and young children. N Engl J Med 2007; 356:685.

4. AS Monto et al. Comparative efficacy of inactivated and live attenuated influenza vaccines. N Engl J Med 2009; 361:1260.

5. CDC. Prevention and control of influenza with vaccines: recommendations of the Advisory Committee on Immunization Practices (ACIP) – United States, 2012-13 influenza season. MMWR 2012; 61:613.

6. K Zaman et al. Effectiveness of maternal influenza immunization in mothers and infants. N Engl J Med 2008; 359:1555.

7. AA Eick et al. Maternal influenza vaccination and effect on influenza virus infection in young infants. Arch Pediatr Adolesc Med 2011; 165:104.

8. KL Nichol et al. Effectiveness of influenza vaccine in the community-dwelling elderly. N Engl J Med 2007; 357:1373.

9. M Loeb et al. Effect of influenza vaccination of children on infection rates in Hutterite communities: a randomized trial. JAMA 2010; 303:943.

10. P Haber et al. Vaccines and Guillain-Barré syndrome. Drug Saf 2009; 32:309.

11. MJ Greenhawt et al. Administering influenza vaccine to egg allergic recipients: a focused practice parameter update. Ann Allergy Asthma

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