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Am Fam Physician. 2009;80(7):744-748

Guideline source: Centers for Disease Control and Prevention, Advisory Committee on Immunization Practices

Literature search described? No

Evidence rating system used? No

Published source:MMWR Recommendations and Reports, July 31 and August 28, 2009 (published correction in Morbidity and Mortality Weekly Report, August 21, 2009)

Worldwide transmission of the novel influenza A (H1N1) virus has continued since June 2009, when the World Health Organization declared a global pandemic. Transmission is likely to persist and may increase in the Northern Hemisphere during the fall and winter of 2009–2010.

Influenza vaccination is the most effective method for preventing influenza and its complications. However, current seasonal influenza vaccines are not likely to provide protection against the H1N1 virus. For this reason, the Advisory Committee on Immunization Practices of the Centers for Disease Control and Prevention (CDC) has published specific recommendations for vaccination against H1N1, in addition to its recommendations for seasonal influenza vaccination.

H1N1 Vaccination

Limited data indicate that seasonal influenza vaccines will not provide protection against the H1N1 virus. Vaccines specific for the H1N1 virus are being produced and are expected to be available in mid-October. Live, attenuated and monovalent inactivated H1N1 vaccine formulations will be available initially. Inactivated vaccines against seasonal and H1N1 viruses can be given simultaneously if different anatomic sites are used. However, simultaneous administration of live, attenuated vaccines is not recommended.

H1N1 vaccination efforts should focus on five target groups:

  • Pregnant women

  • Household contacts and child care providers for infants younger than six months

  • Emergency medical services personnel and other health care workers

  • Persons six months to 24 years of age

  • Persons 25 to 64 years of age with medical conditions that put them at higher risk of influenza-related complications.

Vaccination of persons in these groups should begin as soon as vaccine is available. If vaccine availability is insufficient to meet demands, the following subset of these groups should be prioritized:

  • Pregnant women

  • Household contacts and child care providers for infants younger than six months

  • Emergency medical services personnel and other health care workers who have direct contact with patients or infectious material

  • Children between six months and four years of age

  • Children and adolescents between five and 18 years of age with medical conditions that put them at higher risk of influenza-related complications.

Once vaccine demand has been met among persons in the target groups, vaccination should be offered to all persons 25 to 64 years of age. The risk of infection in persons 65 years and older is less than that in younger persons; therefore, vaccination of older adults is not recommended until vaccine demand among younger age groups is met.

Seasonal Influenza Vaccination

The primary updates to this year's seasonal influenza guidelines include the following recommendations:

  • Vaccination of children six months to 18 years of age should begin as soon as vaccine is available. Vaccination efforts should focus on children six months to four years of age, and on older children with medical conditions that put them at risk of influenza-related complications.

  • Vaccines containing the trivalent vaccine virus strains A/Brisbane/59/2007 (H1N1)-like, A/Brisbane/10/2007 (H3N2)-like, and B/Brisbane/60/2008-like antigens should be used during the 2009–2010 influenza season (Table 1).

VaccineBrand nameManufacturerPresentationMercury content (mcg Hg per 0.5-mL dose)Approved agesNumber of doses requiredRoute of administration
TIV*FluzoneSanofi Pasteur0.25-mL prefilled syringe06 to 35 months1 or 2IM
0.5-mL prefilled syringe0≥ 36 months1 or 2IM
0.5-mL vial0≥ 36 months1 or 2IM
5.0-mL multidose vial25≥ 6 months1 or 2IM
TIV*FluvirinNovartis Vaccines0.5-mL prefilled syringe< 1.0≥ 4 years1 or 2IM
5.0-mL multidose vial25≥ 4 years1 or 2IM
TIV*FluarixGlaxoSmithKline0.5-mL prefilled syringe0≥ 18 years1IM
TIV*FlulavalGlaxoSmithKline5.0-mL multidose vial25≥ 18 years1IM
TIV*AfluriaCSL Biotherapies0.5-mL prefilled syringe0≥ 18 years1IM
5.0-mL multidose vial25≥ 18 years1IM
LAIV§FlumistMedimmune0.2-mL sprayer02 to 49 years1 or 2Intranasal

Healthy, nonpregnant persons two to 49 years of age can choose to receive trivalent inactivated influenza vaccine (TIV) or live, attenuated influenza vaccine (LAIV; Table 2). Some TIV formulations are licensed for use in children as young as six months; TIV also is licensed for use in persons with high-risk conditions. LAIV is licensed for use only in persons two to 49 years of age, and the safety of LAIV has not been established in persons with certain medical conditions. All children six months to eight years of age who have not previously been vaccinated with at least one dose of LAIV or TIV should receive two doses of vaccine in the same season, with a single dose during subsequent seasons.

Influenza vaccine should be provided to all persons who want to reduce their risk of infection or of transmitting influenza to others. However, an emphasis should be placed on vaccinating patients at higher risk of influenza infection or complications, including childrensix months to 18 years of age, persons 50 years and older, and other adults at risk of medical complications from influenza or more likely to require medical care. Persons who live with or care for persons at high risk of influenza-related complications, including caregivers for children younger than six months, should receive influenza vaccine annually.

FactorLAIVTIV
Route of administrationIntranasal sprayIntramuscular injection
Number of included virus strains33
(2 influenza A, 1 influenza B)(2 influenza A, 1 influenza B)
Frequency of updates to vaccine virus strainsAnnuallyAnnually
Frequency of administrationAnnually*Annually*
Approved ages2 to 49 years6 months and older
Interval between doses for children 6 months to 8 years of age who are receiving vaccine for the first time4 weeks4 weeks
Can be administered to persons at risk of influenza-related complicationsNoYes
Can be administered to children with asthma or children 2 to 4 years of age with a history of wheezing during the preceding yearNoYes
Can be administered to close contacts of immunosuppressed persons who do not require a protective environmentYesYes
Can be administered to close contacts of immunosuppressed persons who require a protective environment (e.g., hematopoietic stem cell transplant recipients)NoYes
Can be administered to close contacts of persons at high risk, but who are not severely immunosuppressedYesYes
Can be simultaneously administered with other vaccinesYes§Yes
If not simultaneously administered, can be administered within 4 weeks of another live vaccinePrudent to space 4 weeks apartYes
If not simultaneously administered, can be administered within 4 weeks of an inactivated vaccineYesYes

Antiviral Agents

Four influenza antiviral agents are licensed in the United States: amantadine (Symmetrel), rimantadine (Flumadine), zanamivir (Relenza), and oseltamivir (Tamiflu). The CDC has published interim recommendations for antiviral treatment and chemoprophylaxis of influenza (http://www.cdc.gov/H1N1flu/recommendations.htm). Updates will likely be published as the influenza season progresses. The interim guidelines call for oseltamivir and zanamivir to be used as treatment for all persons with suspected or confirmed influenza who are likely to require hospitalization or are at higher risk for complications, or who present with warning signs of lower respiratory tract illness. All other patients with influenza generally do not require antiviral treatment.

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