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Updated 2006 Influenza Vaccination Recommendations Released

By Clarence Lam and Luciana Borio, M.D., July 5, 2006

On June 26, 2006, the Advisory Committee on Immunization Practices (ACIP) issued updated recommendations for use of seasonal influenza vaccine and antiviral pharmaceuticals [1].

Table 1: ACIP 2006 Recommendations for Annual Influenza Vaccination

Persons at high risk for influenza-related complications and severe disease should be vaccinated, including: 

  • Children aged 6 months to 59 months
  • Women who will be pregnant during influenza season
  • Persons aged 50 years and older
  • Persons of any age with certain chronic conditions, including: cardiopulmonary disease            (including asthma), metabolic diseases (including diabetes mellitus), renal insufficiency,    hemoglobinopathies, immunodeficiency, conditions that can compromise respiratory function or the handling of respiratory secretions, or who receive chronic aspirin therapy

Persons who live with or care for persons at high risk should be vaccinated, including: 

  • Household contacts who have frequent contact with persons at high risk and who can transmit influenza to those persons at high risk
  • Out-of-home caregivers of persons at high risk
  • Healthcare workers

The principle changes of relevance to clinicians are summarized below: 

1. Target groups for influenza vaccination is extended: Although rates of serious illness and death are highest for persons older than 65 years, younger than 2 years, and with certain chronic medical conditions (see table above), overall rates of influenza infection are highest among children. Prior recommendations called for the vaccination of children aged 6 months to 23 months, but they have been extended to include children up to 59 months, as well as their household contacts and out-of-home caregivers.

2. Children should receive 2 doses of vaccine: Recently published studies have shown that vaccine effectiveness is much lower among previously unvaccinated children under age 9 who receive one dose of vaccine compared to similarly-aged children who receive two doses [2, 3]. Based on this research, ACIP recommends that all previously unvaccinated children aged 6 months to 9 years receive two doses of live attenuated or trivalent inactivated influenza vaccine.

  • Children who are 6 months to 9 years old who receive trivalent inactivated influenza vaccine (TIV) should have a booster dose of TIV administered >1 month after the initial dose, before the onset of influenza season, if possible.
  • Children aged 5 up to 9 years who receive live attenuated influenza vaccine (LAIV) should have a second dose of LAIV 6 to 10 weeks after the initial dose, before the influenza season, if possible.
  • If a child under age 9 received influenza vaccine for the first time during a previous season but did not receive a second dose of vaccine within the same season, only 1 dose of vaccine should be administered this season.

3. Extended Vaccination Period: Normal vaccine distribution begins annually in September, but ACIP recognizes that the full distribution process is not complete until December and January. Therefore, vaccination should be offered to individuals through December and despite the arrival of documented influenza activity in a community.

4. Restrictions on use of Amantadine and Rimantadine: Data from published material during the past year indicates that circulating influenza viruses are demonstrating a significant degree of resistance to amantadine and rimantadine [4, 5]. Moreover, other research has shown that one-third of patients treated with amantadine or rimantadine have developed drug-resistant influenza viruses [6, 7]. Studies of zanamivir and oseltamivir indicate that resistance to these drugs occurs less frequently, and thus they are currently recommended for use in instances when antiviral treatment or chemoprophylaxis are indicated [8, 9]. Oseltamivir is approved for treatment or prophylaxis of influenza in persons >1 year. Zanamivir is approved for treatment in persons >7 years, and prophylaxis in persons >5 years.

Table 2: Influenza Vaccines Available in the U.S.

Type

Brand name & manufacturer

Approved use

TIV

Fluzone® (sanofi pasteur)

Approved for persons >6 months

FluvirinTM (Novartis, former Chiron)

Approved for persons >4 years

FLUARIXTM (GSK)

Approved for persons >18 years

LAIV

FluMistTM (MedImmune)

Approved for healthy persons 5 to 49 years

Conclusion

The current U.S. influenza vaccine supply is fragile due to several factors: 1) the limited number of U.S.-licensed manufacturers; 2) an egg-based production system with limited surge capacity; and 3) above all, uncertainty regarding annual demand for vaccination. Expanding the target groups recommended for annual vaccination is a key step toward  ensuring steady demand. It is also critical for pandemic preparedness since pandemic vaccine supply will be directly linked to existing vaccine manufacturing capacity.

References

  1. Smith NM, Bresee JS, Shay DK, et al. Prevention and control of influenza. Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep. 2006; 55(Early Release):1-41.

  2. Ritzwoller DP, Bridges CB, Shetterly S, et al. Effectiveness of the 2003-2004 influenza vaccine among children 6 months to 8 years of age, with 1 vs 2 doses. Pediatrics 2005;116:153-9.

  3. Neuzil KM, Jackson LA, Nelson J, et al. Immunogenicity and reactogenicity of one versus two doses of trivalent inactivated influenza vaccine in vaccine-naïve 5-8-year-old children. J Infect Dis. In press 2006.

  4. CDC. High levels of adamantane resistance among influenza A (H3N2) viruses and interim guidelines for use of antiviral agents---United States, 2005-06 influenza season. MMWR 2006;55:44-6.

  5. Bright RA, Shay DK, Shu B, et al. Adamantane resistance among influenza A viruses isolated early during the 2005-2006 influenza season in the United States. JAMA 2006;295:891-4.

  6. Hall CB, Dolin R, Gala CL, et al. Children with influenza A infection: treatment with rimantadine. Pediatrics 1987;80:275-82.

  7. Saito R, Oshitani H, Masuda H, et al. Detection of amantadine-resistant influenza A virus strains in nursing homes by PCR-restriction fragment length polymorphism analysis with nasopharyngeal swabs. J Clin Microbiol 2002;40:84-8.

  8. Roche Laboratories I. Tamiflu (oseltamivir phosphate) capsules and oral suspension [Product information]. Nutley, NJ: Roche Laboratories, Inc.; 2005.

  9. Barnett JM, Cadman A, Gor D, et al. Zanamivir susceptibility monitoring and characterization of influenza virus clinical isolates obtained during phase II clinical efficacy studies. Antimicrob Agents Chemother 2000;44:78-87.